chore(dashboard/stats): add vega depencency

mod/dashboard/app/vega.js

@@ -0,0 +1,6970 @@
+vg = (function(d3, topojson) { // take d3 & topojson as imports
+  var vg = {
+    version:  "1.3.2", // semantic versioning
+    d3:       d3,      // stash d3 for use in property functions
+    topojson: topojson // stash topojson similarly
+  };
+// type checking functions
+var toString = Object.prototype.toString;
+
+vg.isObject = function(obj) {
+  return obj === Object(obj);
+};
+
+vg.isFunction = function(obj) {
+  return toString.call(obj) == '[object Function]';
+};
+
+vg.isString = function(obj) {
+  return toString.call(obj) == '[object String]';
+};
+  
+vg.isArray = Array.isArray || function(obj) {
+  return toString.call(obj) == '[object Array]';
+};
+
+vg.isNumber = function(obj) {
+  return toString.call(obj) == '[object Number]';
+};
+
+vg.isBoolean = function(obj) {
+  return toString.call(obj) == '[object Boolean]';
+};
+
+vg.isTree = function(obj) {
+  return vg.isArray(obj) && obj.__vgtree__;
+};
+
+vg.number = function(s) { return +s; };
+
+vg.boolean = function(s) { return !!s; };
+
+// utility functions
+
+vg.identity = function(x) { return x; };
+
+vg.extend = function(obj) {
+  for (var x, name, i=1, len=arguments.length; i<len; ++i) {
+    x = arguments[i];
+    for (name in x) { obj[name] = x[name]; }
+  }
+  return obj;
+};
+
+vg.duplicate = function(obj) {
+  return JSON.parse(JSON.stringify(obj));
+};
+
+vg.field = function(f) {
+  return f.split("\\.")
+    .map(function(d) { return d.split("."); })
+    .reduce(function(a, b) {
+      if (a.length) { a[a.length-1] += "." + b.shift(); }
+      a.push.apply(a, b);
+      return a;
+    }, []);
+};
+
+vg.accessor = function(f) {
+  var s;
+  return (vg.isFunction(f) || f==null)
+    ? f : vg.isString(f) && (s=vg.field(f)).length > 1
+    ? function(x) { return s.reduce(function(x,f) { return x[f]; }, x); }
+    : function(x) { return x[f]; };
+};
+
+vg.comparator = function(sort) {
+  var sign = [];
+  if (sort === undefined) sort = [];
+  sort = vg.array(sort).map(function(f) {
+    var s = 1;
+    if      (f[0] === "-") { s = -1; f = f.slice(1); }
+    else if (f[0] === "+") { s = +1; f = f.slice(1); }
+    sign.push(s);
+    return vg.accessor(f);
+  });
+  return function(a,b) {
+    var i, n, f, x, y;
+    for (i=0, n=sort.length; i<n; ++i) {
+      f = sort[i]; x = f(a); y = f(b);
+      if (x < y) return -1 * sign[i];
+      if (x > y) return sign[i];
+    }
+    return 0;
+  };
+};
+
+vg.cmp = function(a, b) { return a<b ? -1 : a>b ? 1 : 0; };
+
+vg.numcmp = function(a, b) { return a - b; };
+
+vg.array = function(x) {
+  return x != null ? (vg.isArray(x) ? x : [x]) : [];
+};
+
+vg.values = function(x) {
+  return (vg.isObject(x) && !vg.isArray(x) && x.values) ? x.values : x;
+};
+
+vg.str = function(x) {
+  return vg.isArray(x) ? "[" + x.map(vg.str) + "]"
+    : vg.isObject(x) ? JSON.stringify(x)
+    : vg.isString(x) ? ("'"+vg_escape_str(x)+"'") : x;
+};
+
+var escape_str_re = /(^|[^\\])'/g;
+
+function vg_escape_str(x) {
+  return x.replace(escape_str_re, "$1\\'");
+}
+
+vg.keys = function(x) {
+  var keys = [];
+  for (var key in x) keys.push(key);
+  return keys;
+};
+
+vg.unique = function(data, f, results) {
+  if (!vg.isArray(data) || data.length==0) return [];
+  f = f || vg.identity;
+  results = results || [];
+  for (var v, i=0, n=data.length; i<n; ++i) {
+    v = f(data[i]);
+    if (results.indexOf(v) < 0) results.push(v);
+  }
+  return results;
+};
+
+vg.minIndex = function(data, f) {
+  if (!vg.isArray(data) || data.length==0) return -1;
+  f = f || vg.identity;
+  var idx = 0, min = f(data[0]), v = min;
+  for (var i=1, n=data.length; i<n; ++i) {
+    v = f(data[i]);
+    if (v < min) { min = v; idx = i; }
+  }
+  return idx;
+};
+
+vg.maxIndex = function(data, f) {
+  if (!vg.isArray(data) || data.length==0) return -1;
+  f = f || vg.identity;
+  var idx = 0, max = f(data[0]), v = max;
+  for (var i=1, n=data.length; i<n; ++i) {
+    v = f(data[i]);
+    if (v > max) { max = v; idx = i; }
+  }
+  return idx;
+};
+
+vg.truncate = function(s, length, pos, word, ellipsis) {
+  var len = s.length;
+  if (len <= length) return s;
+  ellipsis = ellipsis || "...";
+  var l = Math.max(0, length - ellipsis.length);
+
+  switch (pos) {
+    case "left":
+      return ellipsis + (word ? vg_truncateOnWord(s,l,1) : s.slice(len-l));
+    case "middle":
+    case "center":
+      var l1 = Math.ceil(l/2), l2 = Math.floor(l/2);
+      return (word ? vg_truncateOnWord(s,l1) : s.slice(0,l1)) + ellipsis
+        + (word ? vg_truncateOnWord(s,l2,1) : s.slice(len-l2));
+    default:
+      return (word ? vg_truncateOnWord(s,l) : s.slice(0,l)) + ellipsis;
+  }
+}
+
+function vg_truncateOnWord(s, len, rev) {
+  var cnt = 0, tok = s.split(vg_truncate_word_re);
+  if (rev) {
+    s = (tok = tok.reverse())
+      .filter(function(w) { cnt += w.length; return cnt <= len; })
+      .reverse();
+  } else {
+    s = tok.filter(function(w) { cnt += w.length; return cnt <= len; });
+  }
+  return s.length ? s.join("").trim() : tok[0].slice(0, len);
+}
+
+var vg_truncate_word_re = /([\u0009\u000A\u000B\u000C\u000D\u0020\u00A0\u1680\u180E\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u202F\u205F\u2028\u2029\u3000\uFEFF])/;
+
+// Logging
+
+function vg_write(msg) {
+  vg.config.isNode
+    ? process.stderr.write(msg + "\n")
+    : console.log(msg);
+}
+
+vg.log = function(msg) {
+  vg_write("[Vega Log] " + msg);
+};
+
+vg.error = function(msg) {
+  msg = "[Vega Err] " + msg;
+  vg_write(msg);
+  if (typeof alert !== "undefined") alert(msg);
+};vg.config = {};
+
+// are we running in node.js?
+// via timetler.com/2012/10/13/environment-detection-in-javascript/
+vg.config.isNode = typeof exports !== 'undefined' && this.exports !== exports;
+
+// base url for loading external data files
+// used only for server-side operation
+vg.config.baseURL = "";
+
+// version and namepsaces for exported svg
+vg.config.svgNamespace =
+  'version="1.1" xmlns="http://www.w3.org/2000/svg" ' +
+  'xmlns:xlink="http://www.w3.org/1999/xlink"';
+
+// inset padding for automatic padding calculation
+vg.config.autopadInset = 5;
+
+// extensible scale lookup table
+// all d3.scale.* instances also supported
+vg.config.scale = {
+  time: d3.time.scale,
+  utc:  d3.time.scale.utc
+};
+
+// default rendering settings
+vg.config.render = {
+  lineWidth: 1,
+  lineCap:   "butt",
+  font:      "sans-serif",
+  fontSize:  11
+};
+
+// default axis properties
+vg.config.axis = {
+  orient: "bottom",
+  ticks: 10,
+  padding: 3,
+  axisColor: "#000",
+  gridColor: "#d8d8d8",
+  tickColor: "#000",
+  tickLabelColor: "#000",
+  axisWidth: 1,
+  tickWidth: 1,
+  tickSize: 6,
+  tickLabelFontSize: 11,
+  tickLabelFont: "sans-serif",
+  titleColor: "#000",
+  titleFont: "sans-serif",
+  titleFontSize: 11,
+  titleFontWeight: "bold",
+  titleOffset: 35
+};
+
+// default legend properties
+vg.config.legend = {
+  orient: "right",
+  offset: 10,
+  padding: 3,
+  gradientStrokeColor: "#888",
+  gradientStrokeWidth: 1,
+  gradientHeight: 16,
+  gradientWidth: 100,
+  labelColor: "#000",
+  labelFontSize: 10,
+  labelFont: "sans-serif",
+  labelAlign: "left",
+  labelBaseline: "middle",
+  labelOffset: 8,
+  symbolShape: "circle",
+  symbolSize: 50,
+  symbolColor: "#888",
+  symbolStrokeWidth: 1,
+  titleColor: "#000",
+  titleFont: "sans-serif",
+  titleFontSize: 11,
+  titleFontWeight: "bold"
+};
+
+// default color values
+vg.config.color = {
+  rgb: [128, 128, 128],
+  lab: [50, 0, 0],
+  hcl: [0, 0, 50],
+  hsl: [0, 0, 0.5]
+};
+
+// default scale ranges
+vg.config.range = {
+  category10: [
+    "#1f77b4",
+    "#ff7f0e",
+    "#2ca02c",
+    "#d62728",
+    "#9467bd",
+    "#8c564b",
+    "#e377c2",
+    "#7f7f7f",
+    "#bcbd22",
+    "#17becf"
+  ],
+  category20: [
+    "#1f77b4",
+    "#aec7e8",
+    "#ff7f0e",
+    "#ffbb78",
+    "#2ca02c",
+    "#98df8a",
+    "#d62728",
+    "#ff9896",
+    "#9467bd",
+    "#c5b0d5",
+    "#8c564b",
+    "#c49c94",
+    "#e377c2",
+    "#f7b6d2",
+    "#7f7f7f",
+    "#c7c7c7",
+    "#bcbd22",
+    "#dbdb8d",
+    "#17becf",
+    "#9edae5"
+  ],
+  shapes: [
+    "circle",
+    "cross",
+    "diamond",
+    "square",
+    "triangle-down",
+    "triangle-up"
+  ]
+};vg.Bounds = (function() {
+  var bounds = function(b) {
+    this.clear();
+    if (b) this.union(b);
+  };
+  
+  var prototype = bounds.prototype;
+  
+  prototype.clear = function() {
+    this.x1 = +Number.MAX_VALUE;
+    this.y1 = +Number.MAX_VALUE;
+    this.x2 = -Number.MAX_VALUE;
+    this.y2 = -Number.MAX_VALUE;
+    return this;
+  };
+  
+  prototype.set = function(x1, y1, x2, y2) {
+    this.x1 = x1;
+    this.y1 = y1;
+    this.x2 = x2;
+    this.y2 = y2;
+    return this;
+  };
+
+  prototype.add = function(x, y) {
+    if (x < this.x1) this.x1 = x;
+    if (y < this.y1) this.y1 = y;
+    if (x > this.x2) this.x2 = x;
+    if (y > this.y2) this.y2 = y;
+    return this;
+  };
+
+  prototype.expand = function(d) {
+    this.x1 -= d;
+    this.y1 -= d;
+    this.x2 += d;
+    this.y2 += d;
+    return this;
+  };
+  
+  prototype.round = function() {
+    this.x1 = Math.floor(this.x1);
+    this.y1 = Math.floor(this.y1);
+    this.x2 = Math.ceil(this.x2);
+    this.y2 = Math.ceil(this.y2);
+    return this;
+  };
+
+  prototype.translate = function(dx, dy) {
+    this.x1 += dx;
+    this.x2 += dx;
+    this.y1 += dy;
+    this.y2 += dy;
+    return this;
+  };
+  
+  prototype.rotate = function(angle, x, y) {
+    var cos = Math.cos(angle),
+        sin = Math.sin(angle),
+        cx = x - x*cos + y*sin,
+        cy = y - x*sin - y*cos,
+        x1 = this.x1, x2 = this.x2,
+        y1 = this.y1, y2 = this.y2;
+
+    return this.clear()
+      .add(cos*x1 - sin*y1 + cx,  sin*x1 + cos*y1 + cy)
+      .add(cos*x1 - sin*y2 + cx,  sin*x1 + cos*y2 + cy)
+      .add(cos*x2 - sin*y1 + cx,  sin*x2 + cos*y1 + cy)
+      .add(cos*x2 - sin*y2 + cx,  sin*x2 + cos*y2 + cy);
+  }
+
+  prototype.union = function(b) {
+    if (b.x1 < this.x1) this.x1 = b.x1;
+    if (b.y1 < this.y1) this.y1 = b.y1;
+    if (b.x2 > this.x2) this.x2 = b.x2;
+    if (b.y2 > this.y2) this.y2 = b.y2;
+    return this;
+  };
+
+  prototype.encloses = function(b) {
+    return b && (
+      this.x1 <= b.x1 &&
+      this.x2 >= b.x2 &&
+      this.y1 <= b.y1 &&
+      this.y2 >= b.y2
+    );
+  };
+
+  prototype.intersects = function(b) {
+    return b && !(
+      this.x2 < b.x1 ||
+      this.x1 > b.x2 ||
+      this.y2 < b.y1 ||
+      this.y1 > b.y2
+    );
+  };
+
+  prototype.contains = function(x, y) {
+    return !(
+      x < this.x1 ||
+      x > this.x2 ||
+      y < this.y1 ||
+      y > this.y2
+    );
+  };
+
+  prototype.width = function() {
+    return this.x2 - this.x1;
+  };
+
+  prototype.height = function() {
+    return this.y2 - this.y1;
+  };
+
+  return bounds;
+})();vg.Gradient = (function() {
+
+  function gradient(type) {
+    this.id = "grad_" + (vg_gradient_id++);
+    this.type = type || "linear";
+    this.stops = [];
+    this.x1 = 0;
+    this.x2 = 1;
+    this.y1 = 0;
+    this.y2 = 0;
+  };
+
+  var prototype = gradient.prototype;
+
+  prototype.stop = function(offset, color) {
+    this.stops.push({
+      offset: offset,
+      color: color
+    });
+    return this;
+  };
+  
+  return gradient;
+})();
+
+var vg_gradient_id = 0;vg.canvas = {};vg.canvas.path = (function() {
+
+  // Path parsing and rendering code taken from fabric.js -- Thanks!
+  var cmdLength = { m:2, l:2, h:1, v:1, c:6, s:4, q:4, t:2, a:7 },
+      re = [/([MLHVCSQTAZmlhvcsqtaz])/g, /###/, /(\d)-/g, /\s|,|###/];
+
+  function parse(path) {
+    var result = [],
+        currentPath,
+        chunks,
+        parsed;
+
+    // First, break path into command sequence
+    path = path.slice().replace(re[0], '###$1').split(re[1]).slice(1);
+
+    // Next, parse each command in turn
+    for (var i=0, j, chunksParsed, len=path.length; i<len; i++) {
+      currentPath = path[i];
+      chunks = currentPath.slice(1).trim().replace(re[2],'$1###-').split(re[3]);
+      chunksParsed = [currentPath.charAt(0)];
+
+      for (var j = 0, jlen = chunks.length; j < jlen; j++) {
+        parsed = parseFloat(chunks[j]);
+        if (!isNaN(parsed)) {
+          chunksParsed.push(parsed);
+        }
+      }
+
+      var command = chunksParsed[0].toLowerCase(),
+          commandLength = cmdLength[command];
+
+      if (chunksParsed.length - 1 > commandLength) {
+        for (var k = 1, klen = chunksParsed.length; k < klen; k += commandLength) {
+          result.push([ chunksParsed[0] ].concat(chunksParsed.slice(k, k + commandLength)));
+        }
+      }
+      else {
+        result.push(chunksParsed);
+      }
+    }
+
+    return result;
+  }
+
+  function drawArc(g, x, y, coords, bounds, l, t) {
+    var rx = coords[0];
+    var ry = coords[1];
+    var rot = coords[2];
+    var large = coords[3];
+    var sweep = coords[4];
+    var ex = coords[5];
+    var ey = coords[6];
+    var segs = arcToSegments(ex, ey, rx, ry, large, sweep, rot, x, y);
+    for (var i=0; i<segs.length; i++) {
+      var bez = segmentToBezier.apply(null, segs[i]);
+      g.bezierCurveTo.apply(g, bez);
+      bounds.add(bez[0]-l, bez[1]-t);
+      bounds.add(bez[2]-l, bez[3]-t);
+      bounds.add(bez[4]-l, bez[5]-t);
+    }
+  }
+
+  function boundArc(x, y, coords, bounds) {
+    var rx = coords[0];
+    var ry = coords[1];
+    var rot = coords[2];
+    var large = coords[3];
+    var sweep = coords[4];
+    var ex = coords[5];
+    var ey = coords[6];
+    var segs = arcToSegments(ex, ey, rx, ry, large, sweep, rot, x, y);
+    for (var i=0; i<segs.length; i++) {
+      var bez = segmentToBezier.apply(null, segs[i]);
+      bounds.add(bez[0]-l, bez[1]-t);
+      bounds.add(bez[2]-l, bez[3]-t);
+      bounds.add(bez[4]-l, bez[5]-t);
+    }
+  }
+
+  var arcToSegmentsCache = { },
+      segmentToBezierCache = { },
+      join = Array.prototype.join,
+      argsStr;
+
+  // Copied from Inkscape svgtopdf, thanks!
+  function arcToSegments(x, y, rx, ry, large, sweep, rotateX, ox, oy) {
+    argsStr = join.call(arguments);
+    if (arcToSegmentsCache[argsStr]) {
+      return arcToSegmentsCache[argsStr];
+    }
+
+    var th = rotateX * (Math.PI/180);
+    var sin_th = Math.sin(th);
+    var cos_th = Math.cos(th);
+    rx = Math.abs(rx);
+    ry = Math.abs(ry);
+    var px = cos_th * (ox - x) * 0.5 + sin_th * (oy - y) * 0.5;
+    var py = cos_th * (oy - y) * 0.5 - sin_th * (ox - x) * 0.5;
+    var pl = (px*px) / (rx*rx) + (py*py) / (ry*ry);
+    if (pl > 1) {
+      pl = Math.sqrt(pl);
+      rx *= pl;
+      ry *= pl;
+    }
+
+    var a00 = cos_th / rx;
+    var a01 = sin_th / rx;
+    var a10 = (-sin_th) / ry;
+    var a11 = (cos_th) / ry;
+    var x0 = a00 * ox + a01 * oy;
+    var y0 = a10 * ox + a11 * oy;
+    var x1 = a00 * x + a01 * y;
+    var y1 = a10 * x + a11 * y;
+
+    var d = (x1-x0) * (x1-x0) + (y1-y0) * (y1-y0);
+    var sfactor_sq = 1 / d - 0.25;
+    if (sfactor_sq < 0) sfactor_sq = 0;
+    var sfactor = Math.sqrt(sfactor_sq);
+    if (sweep == large) sfactor = -sfactor;
+    var xc = 0.5 * (x0 + x1) - sfactor * (y1-y0);
+    var yc = 0.5 * (y0 + y1) + sfactor * (x1-x0);
+
+    var th0 = Math.atan2(y0-yc, x0-xc);
+    var th1 = Math.atan2(y1-yc, x1-xc);
+
+    var th_arc = th1-th0;
+    if (th_arc < 0 && sweep == 1){
+      th_arc += 2*Math.PI;
+    } else if (th_arc > 0 && sweep == 0) {
+      th_arc -= 2 * Math.PI;
+    }
+
+    var segments = Math.ceil(Math.abs(th_arc / (Math.PI * 0.5 + 0.001)));
+    var result = [];
+    for (var i=0; i<segments; i++) {
+      var th2 = th0 + i * th_arc / segments;
+      var th3 = th0 + (i+1) * th_arc / segments;
+      result[i] = [xc, yc, th2, th3, rx, ry, sin_th, cos_th];
+    }
+
+    return (arcToSegmentsCache[argsStr] = result);
+  }
+
+  function segmentToBezier(cx, cy, th0, th1, rx, ry, sin_th, cos_th) {
+    argsStr = join.call(arguments);
+    if (segmentToBezierCache[argsStr]) {
+      return segmentToBezierCache[argsStr];
+    }
+
+    var a00 = cos_th * rx;
+    var a01 = -sin_th * ry;
+    var a10 = sin_th * rx;
+    var a11 = cos_th * ry;
+
+    var cos_th0 = Math.cos(th0);
+    var sin_th0 = Math.sin(th0);
+    var cos_th1 = Math.cos(th1);
+    var sin_th1 = Math.sin(th1);
+
+    var th_half = 0.5 * (th1 - th0);
+    var sin_th_h2 = Math.sin(th_half * 0.5);
+    var t = (8/3) * sin_th_h2 * sin_th_h2 / Math.sin(th_half);
+    var x1 = cx + cos_th0 - t * sin_th0;
+    var y1 = cy + sin_th0 + t * cos_th0;
+    var x3 = cx + cos_th1;
+    var y3 = cy + sin_th1;
+    var x2 = x3 + t * sin_th1;
+    var y2 = y3 - t * cos_th1;
+
+    return (segmentToBezierCache[argsStr] = [
+      a00 * x1 + a01 * y1,  a10 * x1 + a11 * y1,
+      a00 * x2 + a01 * y2,  a10 * x2 + a11 * y2,
+      a00 * x3 + a01 * y3,  a10 * x3 + a11 * y3
+    ]);
+  }
+
+  function render(g, path, l, t) {
+    var current, // current instruction
+        previous = null,
+        x = 0, // current x
+        y = 0, // current y
+        controlX = 0, // current control point x
+        controlY = 0, // current control point y
+        tempX,
+        tempY,
+        tempControlX,
+        tempControlY,
+        bounds = new vg.Bounds();
+    if (l == undefined) l = 0;
+    if (t == undefined) t = 0;
+
+    g.beginPath();
+  
+    for (var i=0, len=path.length; i<len; ++i) {
+      current = path[i];
+
+      switch (current[0]) { // first letter
+
+        case 'l': // lineto, relative
+          x += current[1];
+          y += current[2];
+          g.lineTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'L': // lineto, absolute
+          x = current[1];
+          y = current[2];
+          g.lineTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'h': // horizontal lineto, relative
+          x += current[1];
+          g.lineTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'H': // horizontal lineto, absolute
+          x = current[1];
+          g.lineTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'v': // vertical lineto, relative
+          y += current[1];
+          g.lineTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'V': // verical lineto, absolute
+          y = current[1];
+          g.lineTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'm': // moveTo, relative
+          x += current[1];
+          y += current[2];
+          g.moveTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'M': // moveTo, absolute
+          x = current[1];
+          y = current[2];
+          g.moveTo(x + l, y + t);
+          bounds.add(x, y);
+          break;
+
+        case 'c': // bezierCurveTo, relative
+          tempX = x + current[5];
+          tempY = y + current[6];
+          controlX = x + current[3];
+          controlY = y + current[4];
+          g.bezierCurveTo(
+            x + current[1] + l, // x1
+            y + current[2] + t, // y1
+            controlX + l, // x2
+            controlY + t, // y2
+            tempX + l,
+            tempY + t
+          );
+          bounds.add(x + current[1], y + current[2]);
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          x = tempX;
+          y = tempY;
+          break;
+
+        case 'C': // bezierCurveTo, absolute
+          x = current[5];
+          y = current[6];
+          controlX = current[3];
+          controlY = current[4];
+          g.bezierCurveTo(
+            current[1] + l,
+            current[2] + t,
+            controlX + l,
+            controlY + t,
+            x + l,
+            y + t
+          );
+          bounds.add(current[1], current[2]);
+          bounds.add(controlX, controlY);
+          bounds.add(x, y);
+          break;
+
+        case 's': // shorthand cubic bezierCurveTo, relative
+          // transform to absolute x,y
+          tempX = x + current[3];
+          tempY = y + current[4];
+          // calculate reflection of previous control points
+          controlX = 2 * x - controlX;
+          controlY = 2 * y - controlY;
+          g.bezierCurveTo(
+            controlX + l,
+            controlY + t,
+            x + current[1] + l,
+            y + current[2] + t,
+            tempX + l,
+            tempY + t
+          );
+          bounds.add(controlX, controlY);
+          bounds.add(x + current[1], y + current[2]);
+          bounds.add(tempX, tempY);
+
+          // set control point to 2nd one of this command
+          // "... the first control point is assumed to be the reflection of the second control point on the previous command relative to the current point."
+          controlX = x + current[1];
+          controlY = y + current[2];
+
+          x = tempX;
+          y = tempY;
+          break;
+
+        case 'S': // shorthand cubic bezierCurveTo, absolute
+          tempX = current[3];
+          tempY = current[4];
+          // calculate reflection of previous control points
+          controlX = 2*x - controlX;
+          controlY = 2*y - controlY;
+          g.bezierCurveTo(
+            controlX + l,
+            controlY + t,
+            current[1] + l,
+            current[2] + t,
+            tempX + l,
+            tempY + t
+          );
+          x = tempX;
+          y = tempY;
+          bounds.add(current[1], current[2]);
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          // set control point to 2nd one of this command
+          // "... the first control point is assumed to be the reflection of the second control point on the previous command relative to the current point."
+          controlX = current[1];
+          controlY = current[2];
+
+          break;
+
+        case 'q': // quadraticCurveTo, relative
+          // transform to absolute x,y
+          tempX = x + current[3];
+          tempY = y + current[4];
+
+          controlX = x + current[1];
+          controlY = y + current[2];
+
+          g.quadraticCurveTo(
+            controlX + l,
+            controlY + t,
+            tempX + l,
+            tempY + t
+          );
+          x = tempX;
+          y = tempY;
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 'Q': // quadraticCurveTo, absolute
+          tempX = current[3];
+          tempY = current[4];
+
+          g.quadraticCurveTo(
+            current[1] + l,
+            current[2] + t,
+            tempX + l,
+            tempY + t
+          );
+          x = tempX;
+          y = tempY;
+          controlX = current[1];
+          controlY = current[2];
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 't': // shorthand quadraticCurveTo, relative
+
+          // transform to absolute x,y
+          tempX = x + current[1];
+          tempY = y + current[2];
+
+          if (previous[0].match(/[QqTt]/) === null) {
+            // If there is no previous command or if the previous command was not a Q, q, T or t,
+            // assume the control point is coincident with the current point
+            controlX = x;
+            controlY = y;
+          }
+          else if (previous[0] === 't') {
+            // calculate reflection of previous control points for t
+            controlX = 2 * x - tempControlX;
+            controlY = 2 * y - tempControlY;
+          }
+          else if (previous[0] === 'q') {
+            // calculate reflection of previous control points for q
+            controlX = 2 * x - controlX;
+            controlY = 2 * y - controlY;
+          }
+
+          tempControlX = controlX;
+          tempControlY = controlY;
+
+          g.quadraticCurveTo(
+            controlX + l,
+            controlY + t,
+            tempX + l,
+            tempY + t
+          );
+          x = tempX;
+          y = tempY;
+          controlX = x + current[1];
+          controlY = y + current[2];
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 'T':
+          tempX = current[1];
+          tempY = current[2];
+
+          // calculate reflection of previous control points
+          controlX = 2 * x - controlX;
+          controlY = 2 * y - controlY;
+          g.quadraticCurveTo(
+            controlX + l,
+            controlY + t,
+            tempX + l,
+            tempY + t
+          );
+          x = tempX;
+          y = tempY;
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 'a':
+          drawArc(g, x + l, y + t, [
+            current[1],
+            current[2],
+            current[3],
+            current[4],
+            current[5],
+            current[6] + x + l,
+            current[7] + y + t
+          ], bounds, l, t);
+          x += current[6];
+          y += current[7];
+          break;
+
+        case 'A':
+          drawArc(g, x + l, y + t, [
+            current[1],
+            current[2],
+            current[3],
+            current[4],
+            current[5],
+            current[6] + l,
+            current[7] + t
+          ], bounds, l, t);
+          x = current[6];
+          y = current[7];
+          break;
+
+        case 'z':
+        case 'Z':
+          g.closePath();
+          break;
+      }
+      previous = current;
+    }
+    return bounds.translate(l, t);
+  }
+
+  function bounds(path, bounds) {
+    var current, // current instruction
+        previous = null,
+        x = 0, // current x
+        y = 0, // current y
+        controlX = 0, // current control point x
+        controlY = 0, // current control point y
+        tempX,
+        tempY,
+        tempControlX,
+        tempControlY;
+
+    for (var i=0, len=path.length; i<len; ++i) {
+      current = path[i];
+
+      switch (current[0]) { // first letter
+
+        case 'l': // lineto, relative
+          x += current[1];
+          y += current[2];
+          bounds.add(x, y);
+          break;
+
+        case 'L': // lineto, absolute
+          x = current[1];
+          y = current[2];
+          bounds.add(x, y);
+          break;
+
+        case 'h': // horizontal lineto, relative
+          x += current[1];
+          bounds.add(x, y);
+          break;
+
+        case 'H': // horizontal lineto, absolute
+          x = current[1];
+          bounds.add(x, y);
+          break;
+
+        case 'v': // vertical lineto, relative
+          y += current[1];
+          bounds.add(x, y);
+          break;
+
+        case 'V': // verical lineto, absolute
+          y = current[1];
+          bounds.add(x, y);
+          break;
+
+        case 'm': // moveTo, relative
+          x += current[1];
+          y += current[2];
+          bounds.add(x, y);
+          break;
+
+        case 'M': // moveTo, absolute
+          x = current[1];
+          y = current[2];
+          bounds.add(x, y);
+          break;
+
+        case 'c': // bezierCurveTo, relative
+          tempX = x + current[5];
+          tempY = y + current[6];
+          controlX = x + current[3];
+          controlY = y + current[4];
+          bounds.add(x + current[1], y + current[2]);
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          x = tempX;
+          y = tempY;
+          break;
+
+        case 'C': // bezierCurveTo, absolute
+          x = current[5];
+          y = current[6];
+          controlX = current[3];
+          controlY = current[4];
+          bounds.add(current[1], current[2]);
+          bounds.add(controlX, controlY);
+          bounds.add(x, y);
+          break;
+
+        case 's': // shorthand cubic bezierCurveTo, relative
+          // transform to absolute x,y
+          tempX = x + current[3];
+          tempY = y + current[4];
+          // calculate reflection of previous control points
+          controlX = 2 * x - controlX;
+          controlY = 2 * y - controlY;
+          bounds.add(controlX, controlY);
+          bounds.add(x + current[1], y + current[2]);
+          bounds.add(tempX, tempY);
+
+          // set control point to 2nd one of this command
+          // "... the first control point is assumed to be the reflection of the second control point on the previous command relative to the current point."
+          controlX = x + current[1];
+          controlY = y + current[2];
+
+          x = tempX;
+          y = tempY;
+          break;
+
+        case 'S': // shorthand cubic bezierCurveTo, absolute
+          tempX = current[3];
+          tempY = current[4];
+          // calculate reflection of previous control points
+          controlX = 2*x - controlX;
+          controlY = 2*y - controlY;
+          x = tempX;
+          y = tempY;
+          bounds.add(current[1], current[2]);
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          // set control point to 2nd one of this command
+          // "... the first control point is assumed to be the reflection of the second control point on the previous command relative to the current point."
+          controlX = current[1];
+          controlY = current[2];
+
+          break;
+
+        case 'q': // quadraticCurveTo, relative
+          // transform to absolute x,y
+          tempX = x + current[3];
+          tempY = y + current[4];
+
+          controlX = x + current[1];
+          controlY = y + current[2];
+
+          x = tempX;
+          y = tempY;
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 'Q': // quadraticCurveTo, absolute
+          tempX = current[3];
+          tempY = current[4];
+
+          x = tempX;
+          y = tempY;
+          controlX = current[1];
+          controlY = current[2];
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 't': // shorthand quadraticCurveTo, relative
+
+          // transform to absolute x,y
+          tempX = x + current[1];
+          tempY = y + current[2];
+
+          if (previous[0].match(/[QqTt]/) === null) {
+            // If there is no previous command or if the previous command was not a Q, q, T or t,
+            // assume the control point is coincident with the current point
+            controlX = x;
+            controlY = y;
+          }
+          else if (previous[0] === 't') {
+            // calculate reflection of previous control points for t
+            controlX = 2 * x - tempControlX;
+            controlY = 2 * y - tempControlY;
+          }
+          else if (previous[0] === 'q') {
+            // calculate reflection of previous control points for q
+            controlX = 2 * x - controlX;
+            controlY = 2 * y - controlY;
+          }
+
+          tempControlX = controlX;
+          tempControlY = controlY;
+
+          x = tempX;
+          y = tempY;
+          controlX = x + current[1];
+          controlY = y + current[2];
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 'T':
+          tempX = current[1];
+          tempY = current[2];
+
+          // calculate reflection of previous control points
+          controlX = 2 * x - controlX;
+          controlY = 2 * y - controlY;
+
+          x = tempX;
+          y = tempY;
+          bounds.add(controlX, controlY);
+          bounds.add(tempX, tempY);
+          break;
+
+        case 'a':
+          boundArc(x, y, [
+            current[1],
+            current[2],
+            current[3],
+            current[4],
+            current[5],
+            current[6] + x,
+            current[7] + y
+          ], bounds);
+          x += current[6];
+          y += current[7];
+          break;
+
+        case 'A':
+          boundArc(x, y, [
+            current[1],
+            current[2],
+            current[3],
+            current[4],
+            current[5],
+            current[6],
+            current[7]
+          ], bounds);
+          x = current[6];
+          y = current[7];
+          break;
+
+        case 'z':
+        case 'Z':
+          break;
+      }
+      previous = current;
+    }
+    return bounds;
+  }
+  
+  function area(items) {
+    var o = items[0];
+    var area = d3.svg.area()
+      .x(function(d) { return d.x; })
+      .y1(function(d) { return d.y; })
+      .y0(function(d) { return d.y + d.height; });
+    if (o.interpolate) area.interpolate(o.interpolate);
+    if (o.tension != null) area.tension(o.tension);
+    return area(items);
+  }
+
+  function line(items) {
+    var o = items[0];
+    var line = d3.svg.line()
+     .x(function(d) { return d.x; })
+     .y(function(d) { return d.y; });
+    if (o.interpolate) line.interpolate(o.interpolate);
+    if (o.tension != null) line.tension(o.tension);
+    return line(items);
+  }
+  
+  return {
+    parse:  parse,
+    render: render,
+    bounds: bounds,
+    area:   area,
+    line:   line
+  };
+  
+})();vg.canvas.marks = (function() {
+
+  var parsePath = vg.canvas.path.parse,
+      renderPath = vg.canvas.path.render,
+      halfpi = Math.PI / 2,
+      sqrt3 = Math.sqrt(3),
+      tan30 = Math.tan(30 * Math.PI / 180),
+      tmpBounds = new vg.Bounds();
+
+  // path generators
+
+  function arcPath(g, o) {
+    var x = o.x || 0,
+        y = o.y || 0,
+        ir = o.innerRadius || 0,
+        or = o.outerRadius || 0,
+        sa = (o.startAngle || 0) - Math.PI/2,
+        ea = (o.endAngle || 0) - Math.PI/2;
+    g.beginPath();
+    if (ir === 0) g.moveTo(x, y);
+    else g.arc(x, y, ir, sa, ea, 0);
+    g.arc(x, y, or, ea, sa, 1);
+    g.closePath();
+  }
+
+  function pathPath(g, o) {
+    if (o.path == null) return;
+    if (!o["path:parsed"]) {
+      o["path:parsed"] = parsePath(o.path);
+    }
+    return renderPath(g, o["path:parsed"], o.x, o.y);
+  }
+
+  function symbolPath(g, o) {
+    g.beginPath();
+    var size = o.size != null ? o.size : 100,
+        x = o.x, y = o.y, r, t, rx, ry;
+
+    if (o.shape == null || o.shape === "circle") {
+      r = Math.sqrt(size/Math.PI);
+      g.arc(x, y, r, 0, 2*Math.PI, 0);
+      g.closePath();
+      return;
+    }
+
+    switch (o.shape) {
+      case "cross":
+        r = Math.sqrt(size / 5) / 2;
+        t = 3*r;
+        g.moveTo(x-t, y-r);
+        g.lineTo(x-r, y-r);
+        g.lineTo(x-r, y-t);
+        g.lineTo(x+r, y-t);
+        g.lineTo(x+r, y-r);
+        g.lineTo(x+t, y-r);
+        g.lineTo(x+t, y+r);
+        g.lineTo(x+r, y+r);
+        g.lineTo(x+r, y+t);
+        g.lineTo(x-r, y+t);
+        g.lineTo(x-r, y+r);
+        g.lineTo(x-t, y+r);
+        break;
+
+      case "diamond":
+        ry = Math.sqrt(size / (2 * tan30));
+        rx = ry * tan30;
+        g.moveTo(x, y-ry);
+        g.lineTo(x+rx, y);
+        g.lineTo(x, y+ry);
+        g.lineTo(x-rx, y);
+        break;
+
+      case "square":
+        t = Math.sqrt(size);
+        r = t / 2;
+        g.rect(x-r, y-r, t, t);
+        break;
+
+      case "triangle-down":
+        rx = Math.sqrt(size / sqrt3);
+        ry = rx * sqrt3 / 2;
+        g.moveTo(x, y+ry);
+        g.lineTo(x+rx, y-ry);
+        g.lineTo(x-rx, y-ry);
+        break;
+
+      case "triangle-up":
+        rx = Math.sqrt(size / sqrt3);
+        ry = rx * sqrt3 / 2;
+        g.moveTo(x, y-ry);
+        g.lineTo(x+rx, y+ry);
+        g.lineTo(x-rx, y+ry);
+    }
+    g.closePath();
+  }
+
+  function areaPath(g, items) {
+    var o = items[0],
+        p = o["path:parsed"] ||
+           (o["path:parsed"] = parsePath(vg.canvas.path.area(items)));
+    renderPath(g, p);
+  }
+
+  function linePath(g, items) {
+    var o = items[0],
+        p = o["path:parsed"] ||
+           (o["path:parsed"] = parsePath(vg.canvas.path.line(items)));
+    renderPath(g, p);
+  }
+
+  function lineStroke(g, items) {
+    var o = items[0],
+        lw = o.strokeWidth,
+        lc = o.strokeCap;
+    g.lineWidth = lw != null ? lw : vg.config.render.lineWidth;
+    g.lineCap   = lc != null ? lc : vg.config.render.lineCap;
+    linePath(g, items);
+  }
+
+  function ruleStroke(g, o) {
+    var x1 = o.x || 0,
+        y1 = o.y || 0,
+        x2 = o.x2 != null ? o.x2 : x1,
+        y2 = o.y2 != null ? o.y2 : y1,
+        lw = o.strokeWidth,
+        lc = o.strokeCap;
+
+    g.lineWidth = lw != null ? lw : vg.config.render.lineWidth;
+    g.lineCap   = lc != null ? lc : vg.config.render.lineCap;
+    g.beginPath();
+    g.moveTo(x1, y1);
+    g.lineTo(x2, y2);
+  }
+
+  // drawing functions
+
+  function drawPathOne(path, g, o, items) {
+    var fill = o.fill, stroke = o.stroke, opac, lc, lw;
+
+    path(g, items);
+
+    opac = o.opacity == null ? 1 : o.opacity;
+    if (opac == 0 || !fill && !stroke) return;
+
+    if (fill) {
+      g.globalAlpha = opac * (o.fillOpacity==null ? 1 : o.fillOpacity);
+      g.fillStyle = color(g, o, fill);
+      g.fill();
+    }
+
+    if (stroke) {
+      lw = (lw = o.strokeWidth) != null ? lw : vg.config.render.lineWidth;
+      if (lw > 0) {
+        g.globalAlpha = opac * (o.strokeOpacity==null ? 1 : o.strokeOpacity);
+        g.strokeStyle = color(g, o, stroke);
+        g.lineWidth = lw;
+        g.lineCap = (lc = o.strokeCap) != null ? lc : vg.config.render.lineCap;
+        g.vgLineDash(o.strokeDash || null);
+        g.vgLineDashOffset(o.strokeDashOffset || 0);
+        g.stroke();
+      }
+    }
+  }
+
+  function drawPathAll(path, g, scene, bounds) {
+    var i, len, item;
+    for (i=0, len=scene.items.length; i<len; ++i) {
+      item = scene.items[i];
+      if (bounds && !bounds.intersects(item.bounds))
+        continue; // bounds check
+      drawPathOne(path, g, item, item);
+    }
+  }
+
+  function drawRect(g, scene, bounds) {
+    if (!scene.items.length) return;
+    var items = scene.items,
+        o, fill, stroke, opac, lc, lw, x, y, w, h;
+
+    for (var i=0, len=items.length; i<len; ++i) {
+      o = items[i];
+      if (bounds && !bounds.intersects(o.bounds))
+        continue; // bounds check
+
+      x = o.x || 0;
+      y = o.y || 0;
+      w = o.width || 0;
+      h = o.height || 0;
+
+      opac = o.opacity == null ? 1 : o.opacity;
+      if (opac == 0) return;
+
+      if (fill = o.fill) {
+        g.globalAlpha = opac * (o.fillOpacity==null ? 1 : o.fillOpacity);
+        g.fillStyle = color(g, o, fill);
+        g.fillRect(x, y, w, h);
+      }
+
+      if (stroke = o.stroke) {
+        lw = (lw = o.strokeWidth) != null ? lw : vg.config.render.lineWidth;
+        if (lw > 0) {
+          g.globalAlpha = opac * (o.strokeOpacity==null ? 1 : o.strokeOpacity);
+          g.strokeStyle = color(g, o, stroke);
+          g.lineWidth = lw;
+          g.lineCap = (lc = o.strokeCap) != null ? lc : vg.config.render.lineCap;
+          g.vgLineDash(o.strokeDash || null);
+          g.vgLineDashOffset(o.strokeDashOffset || 0);
+          g.strokeRect(x, y, w, h);
+        }
+      }
+    }
+  }
+
+  function drawRule(g, scene, bounds) {
+    if (!scene.items.length) return;
+    var items = scene.items,
+        o, stroke, opac, lc, lw, x1, y1, x2, y2;
+
+    for (var i=0, len=items.length; i<len; ++i) {
+      o = items[i];
+      if (bounds && !bounds.intersects(o.bounds))
+        continue; // bounds check
+
+      x1 = o.x || 0;
+      y1 = o.y || 0;
+      x2 = o.x2 != null ? o.x2 : x1;
+      y2 = o.y2 != null ? o.y2 : y1;
+
+      opac = o.opacity == null ? 1 : o.opacity;
+      if (opac == 0) return;
+      
+      if (stroke = o.stroke) {
+        lw = (lw = o.strokeWidth) != null ? lw : vg.config.render.lineWidth;
+        if (lw > 0) {
+          g.globalAlpha = opac * (o.strokeOpacity==null ? 1 : o.strokeOpacity);
+          g.strokeStyle = color(g, o, stroke);
+          g.lineWidth = lw;
+          g.lineCap = (lc = o.strokeCap) != null ? lc : vg.config.render.lineCap;
+          g.vgLineDash(o.strokeDash || null);
+          g.vgLineDashOffset(o.strokeDashOffset || 0);
+          g.beginPath();
+          g.moveTo(x1, y1);
+          g.lineTo(x2, y2);
+          g.stroke();
+        }
+      }
+    }
+  }
+
+  function drawImage(g, scene, bounds) {
+    if (!scene.items.length) return;
+    var renderer = this,
+        items = scene.items, o;
+
+    for (var i=0, len=items.length; i<len; ++i) {
+      o = items[i];
+      if (bounds && !bounds.intersects(o.bounds))
+        continue; // bounds check
+
+      if (!(o.image && o.image.url === o.url)) {
+        o.image = renderer.loadImage(o.url);
+        o.image.url = o.url;
+      }
+
+      var x, y, w, h, opac;
+      w = o.width || (o.image && o.image.width) || 0;
+      h = o.height || (o.image && o.image.height) || 0;
+      x = (o.x||0) - (o.align === "center"
+        ? w/2 : (o.align === "right" ? w : 0));
+      y = (o.y||0) - (o.baseline === "middle"
+        ? h/2 : (o.baseline === "bottom" ? h : 0));
+
+      if (o.image.loaded) {
+        g.globalAlpha = (opac = o.opacity) != null ? opac : 1;
+        g.drawImage(o.image, x, y, w, h);
+      }
+    }
+  }
+
+  function drawText(g, scene, bounds) {
+    if (!scene.items.length) return;
+    var items = scene.items,
+        o, fill, stroke, opac, lw, text, ta, tb;
+
+    for (var i=0, len=items.length; i<len; ++i) {
+      o = items[i];
+      if (bounds && !bounds.intersects(o.bounds))
+        continue; // bounds check
+
+      g.font = vg.scene.fontString(o);
+      g.textAlign = o.align || "left";
+      g.textBaseline = o.baseline || "alphabetic";
+
+      opac = o.opacity == null ? 1 : o.opacity;
+      if (opac == 0) return;
+
+      if (o.angle) {
+        g.save();
+        g.translate(o.x || 0, o.y || 0);
+        g.rotate(o.angle * Math.PI/180);
+        x = o.dx || 0;
+        y = o.dy || 0;
+      } else {
+        x = (o.x || 0) + (o.dx || 0);
+        y = (o.y || 0) + (o.dy || 0);
+      }
+
+      if (fill = o.fill) {
+        g.globalAlpha = opac * (o.fillOpacity==null ? 1 : o.fillOpacity);
+        g.fillStyle = color(g, o, fill);
+        g.fillText(o.text, x, y);
+      }
+
+      if (stroke = o.stroke) {
+        lw = (lw = o.strokeWidth) != null ? lw : 1;
+        if (lw > 0) {
+          g.globalAlpha = opac * (o.strokeOpacity==null ? 1 : o.strokeOpacity);
+          g.strokeStyle = color(o, stroke);
+          g.lineWidth = lw;
+          g.strokeText(o.text, x, y);
+        }
+      }
+
+      if (o.angle) g.restore();
+    }
+  }
+
+  function drawAll(pathFunc) {
+    return function(g, scene, bounds) {
+      drawPathAll(pathFunc, g, scene, bounds);
+    }
+  }
+
+  function drawOne(pathFunc) {
+    return function(g, scene, bounds) {
+      if (!scene.items.length) return;
+      if (bounds && !bounds.intersects(scene.items[0].bounds))
+        return; // bounds check
+      drawPathOne(pathFunc, g, scene.items[0], scene.items);
+    }
+  }
+
+  function drawGroup(g, scene, bounds) {
+    if (!scene.items.length) return;
+    var items = scene.items, group, axes, legends,
+        renderer = this, gx, gy, gb, i, n, j, m;
+
+    drawRect(g, scene, bounds);
+
+    for (i=0, n=items.length; i<n; ++i) {
+      group = items[i];
+      axes = group.axisItems || [];
+      legends = group.legendItems || [];
+      gx = group.x || 0;
+      gy = group.y || 0;
+
+      // render group contents
+      g.save();
+      g.translate(gx, gy);
+      if (bounds) bounds.translate(-gx, -gy);
+      for (j=0, m=axes.length; j<m; ++j) {
+        if (axes[j].def.layer === "back") {
+          renderer.draw(g, axes[j], bounds);
+        }
+      }
+      for (j=0, m=group.items.length; j<m; ++j) {
+        renderer.draw(g, group.items[j], bounds);
+      }
+      for (j=0, m=axes.length; j<m; ++j) {
+        if (axes[j].def.layer !== "back") {
+          renderer.draw(g, axes[j], bounds);
+        }
+      }
+      for (j=0, m=legends.length; j<m; ++j) {
+        renderer.draw(g, legends[j], bounds);
+      }
+      if (bounds) bounds.translate(gx, gy);
+      g.restore();
+    }    
+  }
+
+  function color(g, o, value) {
+    return (value.id)
+      ? gradient(g, value, o.bounds)
+      : value;
+  }
+
+  function gradient(g, p, b) {
+    var w = b.width(),
+        h = b.height(),
+        x1 = b.x1 + p.x1 * w,
+        y1 = b.y1 + p.y1 * h,
+        x2 = b.x1 + p.x2 * w,
+        y2 = b.y1 + p.y2 * h,
+        grad = g.createLinearGradient(x1, y1, x2, y2),
+        stop = p.stops,
+        i, n;
+
+    for (i=0, n=stop.length; i<n; ++i) {
+      grad.addColorStop(stop[i].offset, stop[i].color);
+    }
+    return grad;
+  }
+
+  // hit testing
+
+  function pickGroup(g, scene, x, y, gx, gy) {
+    if (scene.items.length === 0 ||
+        scene.bounds && !scene.bounds.contains(gx, gy)) {
+      return false;
+    }
+    var items = scene.items, subscene, group, hit, dx, dy,
+        handler = this, i, j;
+
+    for (i=items.length; --i>=0;) {
+      group = items[i];
+      dx = group.x || 0;
+      dy = group.y || 0;
+
+      g.save();
+      g.translate(dx, dy);
+      for (j=group.items.length; --j >= 0;) {
+        subscene = group.items[j];
+        if (subscene.interactive === false) continue;
+        hit = handler.pick(subscene, x, y, gx-dx, gy-dy);
+        if (hit) {
+          g.restore();
+          return hit;
+        }
+      }
+      g.restore();
+    }
+
+    return scene.interactive
+      ? pickAll(hitTests.rect, g, scene, x, y, gx, gy)
+      : false;
+  }
+
+  function pickAll(test, g, scene, x, y, gx, gy) {
+    if (!scene.items.length) return false;
+    var o, b, i;
+
+    if (g._ratio !== 1) {
+      x *= g._ratio;
+      y *= g._ratio;
+    }
+
+    for (i=scene.items.length; --i >= 0;) {
+      o = scene.items[i]; b = o.bounds;
+      // first hit test against bounding box
+      if ((b && !b.contains(gx, gy)) || !b) continue;
+      // if in bounding box, perform more careful test
+      if (test(g, o, x, y, gx, gy)) return o;
+    }
+    return false;
+  }
+
+  function pickArea(g, scene, x, y, gx, gy) {
+    if (!scene.items.length) return false;
+    var items = scene.items,
+        o, b, i, di, dd, od, dx, dy;
+
+    b = items[0].bounds;
+    if (b && !b.contains(gx, gy)) return false;
+    if (g._ratio !== 1) {
+      x *= g._ratio;
+      y *= g._ratio;
+    }
+    if (!hitTests.area(g, items, x, y)) return false;
+    return items[0];
+  }
+
+  function pickLine(g, scene, x, y, gx, gy) {
+    if (!scene.items.length) return false;
+    var items = scene.items,
+        o, b, i, di, dd, od, dx, dy;
+
+    b = items[0].bounds;
+    if (b && !b.contains(gx, gy)) return false;
+    if (g._ratio !== 1) {
+      x *= g._ratio;
+      y *= g._ratio;
+    }
+    if (!hitTests.line(g, items, x, y)) return false;
+    return items[0];
+  }
+
+  function pick(test) {
+    return function (g, scene, x, y, gx, gy) {
+      return pickAll(test, g, scene, x, y, gx, gy);
+    };
+  }
+
+  function textHit(g, o, x, y, gx, gy) {
+    if (!o.fontSize) return false;
+    if (!o.angle) return true; // bounds sufficient if no rotation
+
+    var b = vg.scene.bounds.text(o, tmpBounds, true),
+        a = -o.angle * Math.PI / 180,
+        cos = Math.cos(a),
+        sin = Math.sin(a),
+        x = o.x,
+        y = o.y,
+        px = cos*gx - sin*gy + (x - x*cos + y*sin),
+        py = sin*gx + cos*gy + (y - x*sin - y*cos);
+
+    return b.contains(px, py);
+  }
+
+  var hitTests = {
+    text:   textHit,
+    rect:   function(g,o,x,y) { return true; }, // bounds test is sufficient
+    image:  function(g,o,x,y) { return true; }, // bounds test is sufficient
+    rule:   function(g,o,x,y) {
+              if (!g.isPointInStroke) return false;
+              ruleStroke(g,o); return g.isPointInStroke(x,y);
+            },
+    line:   function(g,s,x,y) {
+              if (!g.isPointInStroke) return false;
+              lineStroke(g,s); return g.isPointInStroke(x,y);
+            },
+    arc:    function(g,o,x,y) { arcPath(g,o);  return g.isPointInPath(x,y); },
+    area:   function(g,s,x,y) { areaPath(g,s); return g.isPointInPath(x,y); },
+    path:   function(g,o,x,y) { pathPath(g,o); return g.isPointInPath(x,y); },
+    symbol: function(g,o,x,y) { symbolPath(g,o); return g.isPointInPath(x,y); }
+  };
+
+  return {
+    draw: {
+      group:   drawGroup,
+      area:    drawOne(areaPath),
+      line:    drawOne(linePath),
+      arc:     drawAll(arcPath),
+      path:    drawAll(pathPath),
+      symbol:  drawAll(symbolPath),
+      rect:    drawRect,
+      rule:    drawRule,
+      text:    drawText,
+      image:   drawImage,
+      drawOne: drawOne, // expose for extensibility
+      drawAll: drawAll  // expose for extensibility
+    },
+    pick: {
+      group:   pickGroup,
+      area:    pickArea,
+      line:    pickLine,
+      arc:     pick(hitTests.arc),
+      path:    pick(hitTests.path),
+      symbol:  pick(hitTests.symbol),
+      rect:    pick(hitTests.rect),
+      rule:    pick(hitTests.rule),
+      text:    pick(hitTests.text),
+      image:   pick(hitTests.image),
+      pickAll: pickAll  // expose for extensibility
+    }
+  };
+
+})();vg.canvas.Renderer = (function() {  
+  var renderer = function() {
+    this._ctx = null;
+    this._el = null;
+    this._imgload = 0;
+  };
+  
+  var prototype = renderer.prototype;
+  
+  prototype.initialize = function(el, width, height, pad) {
+    this._el = el;
+    
+    if (!el) return this; // early exit if no DOM element
+
+    // select canvas element
+    var canvas = d3.select(el)
+      .selectAll("canvas.marks")
+      .data([1]);
+    
+    // create new canvas element if needed
+    canvas.enter()
+      .append("canvas")
+      .attr("class", "marks");
+    
+    // remove extraneous canvas if needed
+    canvas.exit().remove();
+    
+    return this.resize(width, height, pad);
+  };
+  
+  prototype.resize = function(width, height, pad) {
+    this._width = width;
+    this._height = height;
+    this._padding = pad;
+    
+    if (this._el) {
+      var canvas = d3.select(this._el).select("canvas.marks");
+
+      // initialize canvas attributes
+      canvas
+        .attr("width", width + pad.left + pad.right)
+        .attr("height", height + pad.top + pad.bottom);
+
+      // get the canvas graphics context
+      var s;
+      this._ctx = canvas.node().getContext("2d");
+      this._ctx._ratio = (s = scaleCanvas(canvas.node(), this._ctx) || 1);
+      this._ctx.setTransform(s, 0, 0, s, s*pad.left, s*pad.top);
+    }
+    
+    initializeLineDash(this._ctx);
+    return this;
+  };
+  
+  function scaleCanvas(canvas, ctx) {
+    // get canvas pixel data
+    var devicePixelRatio = window.devicePixelRatio || 1,
+        backingStoreRatio = (
+          ctx.webkitBackingStorePixelRatio ||
+          ctx.mozBackingStorePixelRatio ||
+          ctx.msBackingStorePixelRatio ||
+          ctx.oBackingStorePixelRatio ||
+          ctx.backingStorePixelRatio) || 1,
+        ratio = devicePixelRatio / backingStoreRatio;
+
+    if (devicePixelRatio !== backingStoreRatio) {
+      var w = canvas.width, h = canvas.height;
+      // set actual and visible canvas size
+      canvas.setAttribute("width", w * ratio);
+      canvas.setAttribute("height", h * ratio);
+      canvas.style.width = w + 'px';
+      canvas.style.height = h + 'px';
+    }
+    return ratio;
+  }
+
+  function initializeLineDash(ctx) {
+    if (ctx.vgLineDash) return; // already set
+
+    var NODASH = [];
+    if (ctx.setLineDash) {
+      ctx.vgLineDash = function(dash) { this.setLineDash(dash || NODASH); };
+      ctx.vgLineDashOffset = function(off) { this.lineDashOffset = off; };
+    } else if (ctx.webkitLineDash !== undefined) {
+    	ctx.vgLineDash = function(dash) { this.webkitLineDash = dash || NODASH; };
+      ctx.vgLineDashOffset = function(off) { this.webkitLineDashOffset = off; };
+    } else if (ctx.mozDash !== undefined) {
+      ctx.vgLineDash = function(dash) { this.mozDash = dash; };
+      ctx.vgLineDashOffset = function(off) { /* unsupported */ };
+    } else {
+      ctx.vgLineDash = function(dash) { /* unsupported */ };
+      ctx.vgLineDashOffset = function(off) { /* unsupported */ };
+    }
+  }
+  
+  prototype.context = function(ctx) {
+    if (ctx) { this._ctx = ctx; return this; }
+    else return this._ctx;
+  };
+  
+  prototype.element = function() {
+    return this._el;
+  };
+  
+  prototype.pendingImages = function() {
+    return this._imgload;
+  };
+
+  function translatedBounds(item, bounds) {
+    var b = new vg.Bounds(bounds);
+    while ((item = item.mark.group) != null) {
+      b.translate(item.x || 0, item.y || 0);
+    }
+    return b;
+  }
+    
+  function getBounds(items) {
+    return !items ? null :
+      vg.array(items).reduce(function(b, item) {
+        return b.union(translatedBounds(item, item.bounds))
+                .union(translatedBounds(item, item['bounds:prev']));
+      }, new vg.Bounds());  
+  }
+  
+  function setBounds(g, bounds) {
+    var bbox = null;
+    if (bounds) {
+      bbox = (new vg.Bounds(bounds)).round();
+      g.beginPath();
+      g.rect(bbox.x1, bbox.y1, bbox.width(), bbox.height());
+      g.clip();
+    }
+    return bbox;
+  }
+  
+  prototype.render = function(scene, items) {
+    var g = this._ctx,
+        pad = this._padding,
+        w = this._width + pad.left + pad.right,
+        h = this._height + pad.top + pad.bottom,
+        bb = null, bb2;
+
+    // setup
+    this._scene = scene;
+    g.save();
+    bb = setBounds(g, getBounds(items));
+    g.clearRect(-pad.left, -pad.top, w, h);
+
+    // render
+    this.draw(g, scene, bb);
+
+    // render again to handle possible bounds change
+    if (items) {
+      g.restore();
+      g.save();
+      bb2 = setBounds(g, getBounds(items));
+      if (!bb.encloses(bb2)) {
+        g.clearRect(-pad.left, -pad.top, w, h);
+        this.draw(g, scene, bb2);
+      }
+    }
+    
+    // takedown
+    g.restore();
+    this._scene = null;
+  };
+  
+  prototype.draw = function(ctx, scene, bounds) {
+    var marktype = scene.marktype,
+        renderer = vg.canvas.marks.draw[marktype];
+    renderer.call(this, ctx, scene, bounds);
+
+    // compute mark-level bounds
+    scene.bounds = scene.items.reduce(function(b, item) {
+      return item.bounds ? b.union(item.bounds) : b;
+    }, scene.bounds || new vg.Bounds());
+  };
+  
+  prototype.renderAsync = function(scene) {
+    // TODO make safe for multiple scene rendering?
+    var renderer = this;
+    if (renderer._async_id) {
+      clearTimeout(renderer._async_id);
+    }
+    renderer._async_id = setTimeout(function() {
+      renderer.render(scene);
+      delete renderer._async_id;
+    }, 50);
+  };
+  
+  prototype.loadImage = function(uri) {
+    var renderer = this,
+        scene = renderer._scene,
+        image = null, url;
+
+    renderer._imgload += 1;
+    if (vg.config.isNode) {
+      image = new (require("canvas").Image)();
+      vg.data.load(uri, function(err, data) {
+        if (err) { vg.error(err); return; }
+        image.src = data;
+        image.loaded = true;
+        renderer._imgload -= 1;
+      });
+    } else {
+      image = new Image();
+      url = vg.config.baseURL + uri;
+      image.onload = function() {
+        vg.log("LOAD IMAGE: "+url);
+        image.loaded = true;
+        renderer._imgload -= 1;
+        renderer.renderAsync(scene);
+      };
+      image.src = url;
+    }
+
+    return image;
+  };
+  
+  return renderer;
+})();vg.canvas.Handler = (function() {
+  var handler = function(el, model) {
+    this._active = null;
+    this._handlers = {};
+    if (el) this.initialize(el);
+    if (model) this.model(model);
+  };
+  
+  var prototype = handler.prototype;
+
+  prototype.initialize = function(el, pad, obj) {
+    this._el = d3.select(el).node();
+    this._canvas = d3.select(el).select("canvas.marks").node();
+    this._padding = pad;
+    this._obj = obj || null;
+    
+    // add event listeners
+    var canvas = this._canvas, that = this;
+    events.forEach(function(type) {
+      canvas.addEventListener(type, function(evt) {
+        prototype[type].call(that, evt);
+      });
+    });
+    
+    return this;
+  };
+  
+  prototype.padding = function(pad) {
+    this._padding = pad;
+    return this;
+  };
+  
+  prototype.model = function(model) {
+    if (!arguments.length) return this._model;
+    this._model = model;
+    return this;
+  };
+
+  prototype.handlers = function() {
+    var h = this._handlers;
+    return vg.keys(h).reduce(function(a, k) {
+      return h[k].reduce(function(a, x) { return (a.push(x), a); }, a);
+    }, []);
+  };
+
+  // setup events
+  var events = [
+    "mousedown",
+    "mouseup",
+    "click",
+    "dblclick",
+    "wheel",
+    "keydown",
+    "keypress",
+    "keyup",
+    "mousewheel"
+  ];
+  events.forEach(function(type) {
+    prototype[type] = function(evt) {
+      this.fire(type, evt);
+    };
+  });
+  events.push("mousemove");
+  events.push("mouseout");
+
+  function eventName(name) {
+    var i = name.indexOf(".");
+    return i < 0 ? name : name.slice(0,i);
+  }
+
+  prototype.mousemove = function(evt) {
+    var pad = this._padding,
+        b = evt.target.getBoundingClientRect(),
+        x = evt.clientX - b.left,
+        y = evt.clientY - b.top,
+        a = this._active,
+        p = this.pick(this._model.scene(), x, y, x-pad.left, y-pad.top);
+
+    if (p === a) {
+      this.fire("mousemove", evt);
+      return;
+    } else if (a) {
+      this.fire("mouseout", evt);
+    }
+    this._active = p;
+    if (p) {
+      this.fire("mouseover", evt);
+    }
+  };
+  
+  prototype.mouseout = function(evt) {
+    if (this._active) {
+      this.fire("mouseout", evt);
+    }
+    this._active = null;
+  };
+
+  // to keep firefox happy
+  prototype.DOMMouseScroll = function(evt) {
+    this.fire("mousewheel", evt);
+  };
+
+  // fire an event
+  prototype.fire = function(type, evt) {
+    var a = this._active,
+        h = this._handlers[type];
+    if (a && h) {
+      for (var i=0, len=h.length; i<len; ++i) {
+        h[i].handler.call(this._obj, evt, a);
+      }
+    }
+  };
+
+  // add an event handler
+  prototype.on = function(type, handler) {
+    var name = eventName(type),
+        h = this._handlers;
+    h = h[name] || (h[name] = []);
+    h.push({
+      type: type,
+      handler: handler
+    });
+    return this;
+  };
+
+  // remove an event handler
+  prototype.off = function(type, handler) {
+    var name = eventName(type),
+        h = this._handlers[name];
+    if (!h) return;
+    for (var i=h.length; --i>=0;) {
+      if (h[i].type !== type) continue;
+      if (!handler || h[i].handler === handler) h.splice(i, 1);
+    }
+    return this;
+  };
+  
+  // retrieve the current canvas context
+  prototype.context = function() {
+    return this._canvas.getContext("2d");
+  };
+  
+  // find the scenegraph item at the current mouse position
+  // returns an array of scenegraph items, from leaf node up to the root
+  // x, y -- the absolute x, y mouse coordinates on the canvas element
+  // gx, gy -- the relative coordinates within the current group
+  prototype.pick = function(scene, x, y, gx, gy) {
+    var g = this.context(),
+        marktype = scene.marktype,
+        picker = vg.canvas.marks.pick[marktype];
+    return picker.call(this, g, scene, x, y, gx, gy);
+  };
+
+  return handler;
+})();vg.svg = {};vg.svg.marks = (function() {
+
+  function x(o)     { return o.x || 0; }
+  function y(o)     { return o.y || 0; }
+  function yh(o)    { return o.y + o.height || 0; }
+  function key(o)   { return o.key; }
+  function size(o)  { return o.size==null ? 100 : o.size; }
+  function shape(o) { return o.shape || "circle"; }
+      
+  var arc_path    = d3.svg.arc(),
+      area_path   = d3.svg.area().x(x).y1(y).y0(yh),
+      line_path   = d3.svg.line().x(x).y(y),
+      symbol_path = d3.svg.symbol().type(shape).size(size);
+  
+  var mark_id = 0;
+  
+  var textAlign = {
+    "left":   "start",
+    "center": "middle",
+    "right":  "end"
+  };
+  
+  var styles = {
+    "fill":             "fill",
+    "fillOpacity":      "fill-opacity",
+    "stroke":           "stroke",
+    "strokeWidth":      "stroke-width",
+    "strokeOpacity":    "stroke-opacity",
+    "strokeCap":        "stroke-linecap",
+    "strokeDash":       "stroke-dasharray",
+    "strokeDashOffset": "stroke-dashoffset",
+    "opacity":          "opacity"
+  };
+  var styleProps = vg.keys(styles);
+
+  function style(d) {
+    var i, n, prop, name, value,
+        o = d.mark ? d : d.length ? d[0] : null;
+    if (o === null) return;
+
+    for (i=0, n=styleProps.length; i<n; ++i) {
+      prop = styleProps[i];
+      name = styles[prop];
+      value = o[prop];
+
+      if (value == null) {
+        if (name === "fill") this.style.setProperty(name, "none", null);
+        else this.style.removeProperty(name);
+      } else {
+        if (value.id) {
+          // ensure definition is included
+          vg.svg._cur._defs[value.id] = value;
+          value = "url(#" + value.id + ")";
+        }
+        this.style.setProperty(name, value+"", null);
+      }
+    }
+  }
+  
+  function arc(o) {
+    var x = o.x || 0,
+        y = o.y || 0;
+    this.setAttribute("transform", "translate("+x+","+y+")");
+    this.setAttribute("d", arc_path(o));
+  }
+  
+  function area(items) {
+    if (!items.length) return;
+    var o = items[0];
+    area_path
+      .interpolate(o.interpolate || "linear")
+      .tension(o.tension == null ? 0.7 : o.tension);
+    this.setAttribute("d", area_path(items));
+  }
+  
+  function line(items) {
+    if (!items.length) return;
+    var o = items[0];
+    line_path
+      .interpolate(o.interpolate || "linear")
+      .tension(o.tension == null ? 0.7 : o.tension);
+    this.setAttribute("d", line_path(items));
+  }
+  
+  function path(o) {
+    var x = o.x || 0,
+        y = o.y || 0;
+    this.setAttribute("transform", "translate("+x+","+y+")");
+    if (o.path != null) this.setAttribute("d", o.path);
+  }
+
+  function rect(o) {
+    this.setAttribute("x", o.x || 0);
+    this.setAttribute("y", o.y || 0);
+    this.setAttribute("width", o.width || 0);
+    this.setAttribute("height", o.height || 0);
+  }
+
+  function rule(o) {
+    var x1 = o.x || 0,
+        y1 = o.y || 0;
+    this.setAttribute("x1", x1);
+    this.setAttribute("y1", y1);
+    this.setAttribute("x2", o.x2 != null ? o.x2 : x1);
+    this.setAttribute("y2", o.y2 != null ? o.y2 : y1);
+  }
+  
+  function symbol(o) {
+    var x = o.x || 0,
+        y = o.y || 0;
+    this.setAttribute("transform", "translate("+x+","+y+")");
+    this.setAttribute("d", symbol_path(o));
+  }
+  
+  function image(o) {
+    var w = o.width || (o.image && o.image.width) || 0,
+        h = o.height || (o.image && o.image.height) || 0,
+        x = o.x - (o.align === "center"
+          ? w/2 : (o.align === "right" ? w : 0)),
+        y = o.y - (o.baseline === "middle"
+          ? h/2 : (o.baseline === "bottom" ? h : 0)),
+        url = vg.config.baseURL + o.url;
+    
+    this.setAttributeNS("http://www.w3.org/1999/xlink", "href", url);
+    this.setAttribute("x", x);
+    this.setAttribute("y", y);
+    this.setAttribute("width", w);
+    this.setAttribute("height", h);
+  }
+    
+  function fontString(o) {
+    return (o.fontStyle ? o.fontStyle + " " : "")
+      + (o.fontVariant ? o.fontVariant + " " : "")
+      + (o.fontWeight ? o.fontWeight + " " : "")
+      + (o.fontSize != null ? o.fontSize : vg.config.render.fontSize) + "px "
+      + (o.font || vg.config.render.font);
+  }
+  
+  function text(o) {
+    var x = o.x || 0,
+        y = o.y || 0,
+        dx = o.dx || 0,
+        dy = o.dy || 0,
+        a = o.angle || 0,
+        align = textAlign[o.align || "left"],
+        base = o.baseline==="top" ? ".9em"
+             : o.baseline==="middle" ? ".35em" : 0;
+  
+    this.setAttribute("x", x + dx);
+    this.setAttribute("y", y + dy);
+    this.setAttribute("dy", dy);
+    this.setAttribute("text-anchor", align);
+    
+    if (a) this.setAttribute("transform", "rotate("+a+" "+x+","+y+")");
+    else this.removeAttribute("transform");
+    
+    if (base) this.setAttribute("dy", base);
+    else this.removeAttribute("dy");
+    
+    this.textContent = o.text;
+    this.style.setProperty("font", fontString(o), null);
+  }
+  
+  function group(o) {
+    var x = o.x || 0,
+        y = o.y || 0;
+    this.setAttribute("transform", "translate("+x+","+y+")");
+  }
+
+  function group_bg(o) {
+    var w = o.width || 0,
+        h = o.height || 0;
+    this.setAttribute("width", w);
+    this.setAttribute("height", h);
+  }
+
+  function draw(tag, attr, nest) {
+    return function(g, scene, index) {
+      drawMark(g, scene, index, "mark_", tag, attr, nest);
+    };
+  }
+  
+  function drawMark(g, scene, index, prefix, tag, attr, nest) {
+    var data = nest ? [scene.items] : scene.items,
+        evts = scene.interactive===false ? "none" : null,
+        grps = g.node().childNodes,
+        notG = (tag !== "g"),
+        p = (p = grps[index+1]) // +1 to skip group background rect
+          ? d3.select(p)
+          : g.append("g").attr("id", "g"+(++mark_id));
+
+    var id = "#" + p.attr("id"),
+        s = id + " > " + tag,
+        m = p.selectAll(s).data(data),
+        e = m.enter().append(tag);
+
+    if (notG) {
+      p.style("pointer-events", evts);
+      e.each(function(d) {
+        if (d.mark) d._svg = this;
+        else if (d.length) d[0]._svg = this;
+      });
+    } else {
+      e.append("rect").attr("class","background").style("pointer-events",evts);
+    }
+    
+    m.exit().remove();
+    m.each(attr);
+    if (notG) m.each(style);
+    else p.selectAll(s+" > rect.background").each(group_bg).each(style);
+    
+    return p;
+  }
+
+  function drawGroup(g, scene, index, prefix) {    
+    var p = drawMark(g, scene, index, prefix || "group_", "g", group),
+        c = p.node().childNodes, n = c.length, i, j, m;
+    
+    for (i=0; i<n; ++i) {
+      var items = c[i].__data__.items,
+          legends = c[i].__data__.legendItems || [],
+          axes = c[i].__data__.axisItems || [],
+          sel = d3.select(c[i]),
+          idx = 0;
+
+      for (j=0, m=axes.length; j<m; ++j) {
+        if (axes[j].def.layer === "back") {
+          drawGroup.call(this, sel, axes[j], idx++, "axis_");
+        }
+      }
+      for (j=0, m=items.length; j<m; ++j) {
+        this.draw(sel, items[j], idx++);
+      }
+      for (j=0, m=axes.length; j<m; ++j) {
+        if (axes[j].def.layer !== "back") {
+          drawGroup.call(this, sel, axes[j], idx++, "axis_");
+        }
+      }
+      for (j=0, m=legends.length; j<m; ++j) {
+        drawGroup.call(this, sel, legends[j], idx++, "legend_");
+      }
+    }
+  }
+
+  return {
+    update: {
+      group:   rect,
+      area:    area,
+      line:    line,
+      arc:     arc,
+      path:    path,
+      symbol:  symbol,
+      rect:    rect,
+      rule:    rule,
+      text:    text,
+      image:   image
+    },
+    nested: {
+      "area": true,
+      "line": true
+    },
+    style: style,
+    draw: {
+      group:   drawGroup,
+      area:    draw("path", area, true),
+      line:    draw("path", line, true),
+      arc:     draw("path", arc),
+      path:    draw("path", path),
+      symbol:  draw("path", symbol),
+      rect:    draw("rect", rect),
+      rule:    draw("line", rule),
+      text:    draw("text", text),
+      image:   draw("image", image),
+      draw:    draw // expose for extensibility
+    }
+  };
+  
+})();vg.svg.Renderer = (function() {  
+  var renderer = function() {
+    this._svg = null;
+    this._ctx = null;
+    this._el = null;
+    this._defs = {};
+  };
+  
+  var prototype = renderer.prototype;
+  
+  prototype.initialize = function(el, width, height, pad) {
+    this._el = el;
+
+    // remove any existing svg element
+    d3.select(el).select("svg.marks").remove();
+
+    // create svg element and initialize attributes
+    this._svg = d3.select(el)
+      .append("svg")
+      .attr("class", "marks");
+    
+    // set the svg root group
+    this._ctx = this._svg.append("g");
+    
+    return this.resize(width, height, pad);
+  };
+  
+  prototype.resize = function(width, height, pad) {
+    this._width = width;
+    this._height = height;
+    this._padding = pad;
+    
+    this._svg
+      .attr("width", width + pad.left + pad.right)
+      .attr("height", height + pad.top + pad.bottom);
+      
+    this._ctx
+      .attr("transform", "translate("+pad.left+","+pad.top+")");
+
+    return this;
+  };
+  
+  prototype.context = function() {
+    return this._ctx;
+  };
+  
+  prototype.element = function() {
+    return this._el;
+  };
+
+  prototype.updateDefs = function() {
+    var svg = this._svg,
+        all = this._defs,
+        ids = vg.keys(all),
+        defs = svg.select("defs"), grds;
+  
+    // get or create svg defs block
+    if (ids.length===0) { defs.remove(); return; }
+    if (defs.empty()) defs = svg.insert("defs", ":first-child");
+    
+    grds = defs.selectAll("linearGradient").data(ids, vg.identity);
+    grds.enter().append("linearGradient").attr("id", vg.identity);
+    grds.exit().remove();
+    grds.each(function(id) {
+      var def = all[id],
+          grd = d3.select(this);
+  
+      // set gradient coordinates
+      grd.attr({x1: def.x1, x2: def.x2, y1: def.y1, y2: def.y2});
+  
+      // set gradient stops
+      stop = grd.selectAll("stop").data(def.stops);
+      stop.enter().append("stop");
+      stop.exit().remove();
+      stop.attr("offset", function(d) { return d.offset; })
+          .attr("stop-color", function(d) { return d.color; });
+    });
+  };
+  
+  prototype.render = function(scene, items) {
+    vg.svg._cur = this;
+
+    if (items) this.renderItems(vg.array(items));
+    else this.draw(this._ctx, scene, -1);
+    this.updateDefs();
+
+   delete vg.svg._cur;
+  };
+  
+  prototype.renderItems = function(items) {
+    var item, node, type, nest, i, n,
+        marks = vg.svg.marks;
+
+    for (i=0, n=items.length; i<n; ++i) {
+      item = items[i];
+      node = item._svg;
+      type = item.mark.marktype;
+
+      item = marks.nested[type] ? item.mark.items : item;
+      marks.update[type].call(node, item);
+      marks.style.call(node, item);
+    }
+  }
+  
+  prototype.draw = function(ctx, scene, index) {
+    var marktype = scene.marktype,
+        renderer = vg.svg.marks.draw[marktype];
+    renderer.call(this, ctx, scene, index);
+  };
+  
+  return renderer;
+})();vg.svg.Handler = (function() {
+  var handler = function(el, model) {
+    this._active = null;
+    this._handlers = {};
+    if (el) this.initialize(el);
+    if (model) this.model(model);
+  };
+  
+  function svgHandler(handler) {
+    var that = this;
+    return function(evt) {
+      var target = evt.target,
+          item = target.__data__;
+      if (item) {
+        item = item.mark ? item : item[0];
+        handler.call(that._obj, evt, item);
+      }
+    };
+  }
+  
+  function eventName(name) {
+    var i = name.indexOf(".");
+    return i < 0 ? name : name.slice(0,i);
+  }
+  
+  var prototype = handler.prototype;
+
+  prototype.initialize = function(el, pad, obj) {
+    this._el = d3.select(el).node();
+    this._svg = d3.select(el).select("svg.marks").node();
+    this._padding = pad;
+    this._obj = obj || null;
+    return this;
+  };
+  
+  prototype.padding = function(pad) {
+    this._padding = pad;
+    return this;
+  };
+  
+  prototype.model = function(model) {
+    if (!arguments.length) return this._model;
+    this._model = model;
+    return this;
+  };
+  
+  prototype.handlers = function() {
+    var h = this._handlers;
+    return vg.keys(h).reduce(function(a, k) {
+      return h[k].reduce(function(a, x) { return (a.push(x), a); }, a);
+    }, []);
+  };
+
+  // add an event handler
+  prototype.on = function(type, handler) {
+    var name = eventName(type),
+        h = this._handlers,
+        dom = d3.select(this._svg).node();
+        
+    var x = {
+      type: type,
+      handler: handler,
+      svg: svgHandler.call(this, handler)
+    };
+    h = h[name] || (h[name] = []);
+    h.push(x);
+
+    dom.addEventListener(name, x.svg);
+    return this;
+  };
+
+  // remove an event handler
+  prototype.off = function(type, handler) {
+    var name = eventName(type),
+        h = this._handlers[name],
+        dom = d3.select(this._svg).node();
+    if (!h) return;
+    for (var i=h.length; --i>=0;) {
+      if (h[i].type !== type) continue;
+      if (!handler || h[i].handler === handler) {
+        dom.removeEventListener(name, h[i].svg);
+        h.splice(i, 1);
+      }
+    }
+    return this;
+  };
+
+  return handler;
+})();vg.data = {};
+
+vg.data.ingestAll = function(data) {
+  return vg.isTree(data)
+    ? vg_make_tree(vg.data.ingestTree(data[0], data.children))
+    : data.map(vg.data.ingest);
+};
+
+vg.data.ingest = function(datum, index) {
+  return {
+    data: datum,
+    index: index
+  };
+};
+
+vg.data.ingestTree = function(node, children) {
+  var d = vg.data.ingest(node),
+      c = node[children], n, i;
+  if (c && (n = c.length)) {
+    d.values = Array(n);
+    for (i=0; i<n; ++i) {
+      d.values[i] = vg.data.ingestTree(c[i], children);
+    }
+  }
+  return d;
+};
+
+
+function vg_make_tree(d) {
+  d.__vgtree__ = true;
+  d.nodes = function() { return vg_tree_nodes(this, []); };
+  return d;
+}
+
+function vg_tree_nodes(root, nodes) {
+  var c = root.values,
+      n = c ? c.length : 0, i;
+  nodes.push(root);
+  for (i=0; i<n; ++i) { vg_tree_nodes(c[i], nodes); }
+  return nodes;
+}
+
+function vg_data_duplicate(d) {
+  var x=d, i, n;
+  if (vg.isArray(d)) {
+    x = [];
+    for (i=0, n=d.length; i<n; ++i) {
+      x.push(vg_data_duplicate(d[i]));
+    }
+  } else if (vg.isObject(d)) {
+    x = {};
+    for (i in d) {
+      x[i] = vg_data_duplicate(d[i]);
+    }
+  }
+  return x;
+}
+
+vg.data.mapper = function(func) {
+  return function(data) {
+    data.forEach(func);
+    return data;
+  }
+};
+
+vg.data.size = function(size, group) {
+  size = vg.isArray(size) ? size : [0, size];
+  size = size.map(function(d) {
+    return (typeof d === 'string') ? group[d] : d;
+  });
+  return size;
+};vg.data.load = function(uri, callback) {
+  var url = vg_load_hasProtocol(uri) ? uri : vg.config.baseURL + uri;
+  if (vg.config.isNode) {
+    // in node.js, consult url and select file or http
+    var get = vg_load_isFile(url) ? vg_load_file : vg_load_http;
+    get(url, callback);
+  } else {
+    // in browser, use xhr
+    vg_load_xhr(url, callback);
+  }  
+};
+
+var vg_load_protocolRE = /^[A-Za-z]+\:\/\//;
+var vg_load_fileProtocol = "file://";
+
+function vg_load_hasProtocol(url) {
+  return vg_load_protocolRE.test(url);
+}
+
+function vg_load_isFile(url) {
+  return url.indexOf(vg_load_fileProtocol) === 0;
+}
+
+function vg_load_xhr(url, callback) {
+  vg.log("LOAD: " + url);
+  d3.xhr(url, function(err, resp) {
+    if (resp) resp = resp.responseText;
+    callback(err, resp);
+  });
+}
+
+function vg_load_file(file, callback) {
+  vg.log("LOAD FILE: " + file);
+  var idx = file.indexOf(vg_load_fileProtocol);
+  if (idx >= 0) file = file.slice(vg_load_fileProtocol.length);
+  require("fs").readFile(file, callback);
+}
+
+function vg_load_http(url, callback) {
+  vg.log("LOAD HTTP: " + url);
+	var req = require("http").request(url, function(res) {
+    var pos=0, data = new Buffer(parseInt(res.headers['content-length'],10));
+		res.on("error", function(err) { callback(err, null); });
+		res.on("data", function(x) { x.copy(data, pos); pos += x.length; });
+		res.on("end", function() { callback(null, data); });
+	});
+	req.on("error", function(err) { callback(err); });
+	req.end();
+}vg.data.read = (function() {
+  var formats = {},
+      parsers = {
+        "number": vg.number,
+        "boolean": vg.boolean,
+        "date": Date.parse
+      };
+
+  function read(data, format) {
+    var type = (format && format.type) || "json";
+    data = formats[type](data, format);
+    if (format && format.parse) parseValues(data, format.parse);
+    return data;
+  }
+
+  formats.json = function(data, format) {
+    var d = JSON.parse(data);
+    if (format && format.property) {
+      d = vg.accessor(format.property)(d);
+    }
+    return d;
+  };
+
+  formats.csv = function(data, format) {
+    var d = d3.csv.parse(data);
+    return d;
+  };
+
+  formats.tsv = function(data, format) {
+    var d = d3.tsv.parse(data);
+    return d;
+  };
+  
+  formats.topojson = function(data, format) {
+    if (topojson == null) {
+      vg.error("TopoJSON library not loaded.");
+      return [];
+    }    
+    var t = JSON.parse(data), obj = [];
+
+    if (format && format.feature) {
+      obj = (obj = t.objects[format.feature])
+        ? topojson.feature(t, obj).features
+        : (vg.error("Invalid TopoJSON object: "+format.feature), []);
+    } else if (format && format.mesh) {
+      obj = (obj = t.objects[format.mesh])
+        ? [topojson.mesh(t, t.objects[format.mesh])]
+        : (vg.error("Invalid TopoJSON object: " + format.mesh), []);
+    }
+    else { vg.error("Missing TopoJSON feature or mesh parameter."); }
+
+    return obj;
+  };
+  
+  formats.treejson = function(data, format) {
+    var d = [JSON.parse(data)];
+    d.__vgtree__ = true;
+    d.children = format.children || "children";
+    return d;
+  };
+  
+  function parseValues(data, types) {
+    var cols = vg.keys(types),
+        p = cols.map(function(col) { return parsers[types[col]]; }),
+        tree = vg.isTree(data);
+    vg_parseArray(tree ? [data] : data, cols, p, tree);
+  }
+  
+  function vg_parseArray(data, cols, p, tree) {
+    var d, i, j, len, clen;
+    for (i=0, len=data.length; i<len; ++i) {
+      d = data[i];
+      for (j=0, clen=cols.length; j<clen; ++j) {
+        d[cols[j]] = p[j](d[cols[j]]);
+      }
+      if (tree && d.values) parseCollection(d, cols, p, true);
+    }
+  }
+
+  read.formats = formats;
+  read.parse = parseValues;
+  return read;
+})();vg.data.array = function() {
+  var fields = [];
+   
+  function array(data) {
+    return data.map(function(d) {      
+      var list = [];
+      for (var i=0, len=fields.length; i<len; ++i) {
+        list.push(fields[i](d));
+      }
+      return list;
+    });
+  }
+  
+  array.fields = function(fieldList) {
+    fields = vg.array(fieldList).map(vg.accessor);
+    return array;
+  };
+  
+  return array;
+};vg.data.copy = function() {
+  var from = vg.accessor("data"),
+      fields = [],
+      as = null;
+  
+  var copy = vg.data.mapper(function(d) {
+    var src = from(d), i, len,
+        source = fields,
+        target = as || fields;
+    for (i=0, len=fields.length; i<len; ++i) {
+      d[target[i]] = src[fields[i]];
+    }
+    return d;
+  });
+
+  copy.from = function(field) {
+    from = vg.accessor(field);
+    return copy;
+  };
+  
+  copy.fields = function(fieldList) {
+    fields = vg.array(fieldList);
+    return copy;
+  };
+  
+  copy.as = function(fieldList) {
+    as = vg.array(fieldList);
+    return copy;
+  };
+
+  return copy;
+};vg.data.cross = function() {
+  var other = null,
+      nodiag = false,
+      output = {left:"a", right:"b"};
+
+  function cross(data) {
+    var result = [],
+        data2 = other || data,
+        o, i, j, n = data.length;
+
+    for (i=0; i<n; ++i) {
+      for (j=0; j<n; ++j) {
+        if (nodiag && i===j) continue;
+        o = {};
+        o[output.left] = data[i];
+        o[output.right] = data2[j];
+        result.push(o);
+      }
+    }
+    return result;
+  }
+
+  cross["with"] = function(d) {
+    other = d;
+    return cross;
+  };
+  
+  cross.diagonal = function(x) {
+    nodiag = !x;
+    return cross;
+  };
+
+  cross.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) { output[k] = map[k]; }
+    });
+    return cross;
+  };
+
+  return cross;
+};
+vg.data.facet = function() {
+
+  var keys = [],
+      sort = null;
+
+  function facet(data) {    
+    var result = {
+          key: "",
+          keys: [],
+          values: []
+        },
+        map = {}, 
+        vals = result.values,
+        obj, klist, kstr, len, i, j, k, kv, cmp;
+
+    if (keys.length === 0) {
+      // if no keys, skip collation step
+      vals.push(obj = {
+        key: "", keys: [], index: 0,
+        values: sort ? data.slice() : data
+      });
+      if (sort) sort(obj.values);
+      return result;
+    }
+
+    for (i=0, len=data.length; i<len; ++i) {
+      for (k=0, klist=[], kstr=""; k<keys.length; ++k) {
+        kv = keys[k](data[i]);
+        klist.push(kv);
+        kstr += (k>0 ? "|" : "") + String(kv);
+      }
+      obj = map[kstr];
+      if (obj === undefined) {
+        vals.push(obj = map[kstr] = {
+          key: kstr,
+          keys: klist,
+          index: vals.length,
+          values: []
+        });
+      }
+      obj.values.push(data[i]);
+    }
+
+    if (sort) {
+      for (i=0, len=vals.length; i<len; ++i) {
+        sort(vals[i].values);
+      }
+    }
+
+    return result;
+  }
+  
+  facet.keys = function(k) {
+    keys = vg.array(k).map(vg.accessor);
+    return facet;
+  };
+  
+  facet.sort = function(s) {
+    sort = vg.data.sort().by(s);
+    return facet;
+  };
+
+  return facet;
+};vg.data.filter = function() {
+
+  var test = null;
+
+  function filter(data) {
+    return test ? data.filter(test) : data;
+  }
+  
+  filter.test = function(func) {
+    test = vg.isFunction(func) ? func : vg.parse.expr(func);
+    return filter;
+  };
+
+  return filter;
+};vg.data.flatten = function() {
+    
+  function flatten(data) {
+    return flat(data, []);
+  }
+  
+  function flat(data, list) {
+    if (data.values) {
+      for (var i=0, n=data.values.length; i<n; ++i) {
+        flat(data.values[i], list);
+      }
+    } else {
+      list.push(data);
+    }
+    return list;
+  }
+  
+  return flatten;
+};vg.data.fold = function() {
+  var fields = [],
+      accessors = [],
+      output = {
+        key: "key",
+        value: "value"
+      };
+
+  function fold(data) {
+    var values = [],
+        item, i, j, n, m = fields.length;
+
+    for (i=0, n=data.length; i<n; ++i) {
+      item = data[i];
+      for (j=0; j<m; ++j) {
+        var o = {
+          index: values.length,
+          data: item.data
+        };
+        o[output.key] = fields[j];
+        o[output.value] = accessors[j](item);
+        values.push(o);
+      }
+    }
+
+    return values;
+  }  
+
+  fold.fields = function(f) {
+    fields = vg.array(f);
+    accessors = fields.map(vg.accessor);
+    return fold;
+  };
+
+  fold.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return fold;
+  };
+
+  return fold;
+};vg.data.force = function() {
+  var layout = d3.layout.force(),
+      links = null,
+      linkDistance = 20,
+      linkStrength = 1,
+      charge = -30,
+      iterations = 500,
+      size = ["width", "height"],
+      params = [
+        "friction",
+        "theta",
+        "gravity",
+        "alpha"
+      ];
+
+  function force(data, db, group) {    
+    layout
+      .size(vg.data.size(size, group))
+      .nodes(data);
+      
+    if (links && db[links]) {
+      layout.links(db[links]);
+    }
+
+    layout.start();      
+    for (var i=0; i<iterations; ++i) {
+      layout.tick();
+    }
+    layout.stop();
+    
+    return data;
+  }
+
+  force.links = function(dataSetName) {
+    links = dataSetName;
+    return force;
+  };
+  
+  force.size = function(sz) {
+    size = sz;
+    return force;
+  };
+       
+  force.linkDistance = function(field) {
+    linkDistance = typeof field === 'number'
+      ? field
+      : vg.accessor(field);
+    layout.linkDistance(linkDistance);
+    return force;
+  };
+
+  force.linkStrength = function(field) {
+    linkStrength = typeof field === 'number'
+      ? field
+      : vg.accessor(field);
+    layout.linkStrength(linkStrength);
+    return force;
+  };
+  
+  force.charge = function(field) {
+    charge = typeof field === 'number'
+      ? field
+      : vg.accessor(field);
+    layout.charge(charge);
+    return force;
+  };
+  
+  force.iterations = function(iter) {
+    iterations = iter;
+    return force;
+  };
+
+  params.forEach(function(name) {
+    force[name] = function(x) {
+      layout[name](x);
+      return force;
+    }
+  });
+
+  return force;
+};vg.data.formula = (function() {
+  
+  return function() {
+    var field = null,
+        expr = vg.identity;
+  
+    var formula = vg.data.mapper(function(d, i, list) {
+      if (field) d[field] = expr.call(null, d, i, list);
+      return d;
+    });
+
+    formula.field = function(name) {
+      field = name;
+      return formula;
+    };
+  
+    formula.expr = function(func) {
+      expr = vg.isFunction(func) ? func : vg.parse.expr(func);
+      return formula;
+    };
+
+    return formula;
+  };
+})();vg.data.geo = (function() {
+  var params = [
+    "center",
+    "scale",
+    "translate",
+    "rotate",
+    "precision",
+    "clipAngle"
+  ];
+
+  function geo() {
+    var opt = {},
+        projection = "mercator",
+        func = d3.geo[projection](),
+        lat = vg.identity,
+        lon = vg.identity,
+        output = {
+          "x": "x",
+          "y": "y"
+        };
+    
+    var map = vg.data.mapper(function(d) {
+      var ll = [lon(d), lat(d)],
+          xy = func(ll);
+      d[output.x] = xy[0];
+      d[output.y] = xy[1];
+      return d;
+    });
+
+    map.func = function() {
+      return func;
+    };
+        
+    map.projection = function(p) {
+      if (projection !== p) {
+        projection = p;
+        func = d3.geo[projection]();
+        for (var name in opt) {
+          func[name](opt[name]);
+        }
+      }
+      return map;
+    };
+
+    params.forEach(function(name) {
+      map[name] = function(x) {
+        opt[name] = x;
+        func[name](x);
+        return map;
+      }
+    });
+    
+    map.lon = function(field) {
+      lon = vg.accessor(field);
+      return map;
+    };
+
+    map.lat = function(field) {
+      lat = vg.accessor(field);
+      return map;
+    };
+    
+    map.output = function(map) {
+      vg.keys(output).forEach(function(k) {
+        if (map[k] !== undefined) {
+          output[k] = map[k];
+        }
+      });
+      return map;
+    };
+    
+    
+    return map;
+  };
+  
+  geo.params = params;
+  return geo;
+})();vg.data.geopath = function() {
+  var geopath = d3.geo.path().projection(d3.geo.mercator()),
+      projection = "mercator",
+      geojson = vg.identity,
+      opt = {},
+      output = {"path": "path"};
+
+  var map = vg.data.mapper(function(d) {
+    d[output.path] = geopath(geojson(d));
+    return d;
+  });
+  
+  map.projection = function(proj) {
+    if (projection !== proj) {
+      projection = proj;
+      var p = d3.geo[projection]();
+      for (var name in opt) {
+        p[name](opt[name]);
+      }
+      geopath.projection(p);
+    }
+    return map;
+  };
+  
+  vg.data.geo.params.forEach(function(name) {
+    map[name] = function(x) {
+      opt[name] = x;
+      (geopath.projection())[name](x);
+      return map;
+    }
+  });
+   
+  map.value = function(field) {
+    geojson = vg.accessor(field);
+    return map;
+  };
+
+  map.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return map;
+  };
+
+  return map;
+};vg.data.link = function() {
+  var shape = "line",
+      source = vg.accessor("source"),
+      target = vg.accessor("target"),
+      tension = 0.2,
+      output = {"path": "path"};
+  
+  function line(d) {
+    var s = source(d),
+        t = target(d);
+    return "M" + s.x + "," + s.y 
+         + "L" + t.x + "," + t.y;
+  }
+
+  function curve(d) {
+    var s = source(d),
+        t = target(d),
+        dx = t.x - s.x,
+        dy = t.y - s.y,
+        ix = tension * (dx + dy),
+        iy = tension * (dy - dx);
+    return "M" + s.x + "," + s.y
+         + "C" + (s.x+ix) + "," + (s.y+iy)
+         + " " + (t.x+iy) + "," + (t.y-ix)
+         + " " + t.x + "," + t.y;
+  }
+  
+  function diagonalX(d) {
+    var s = source(d),
+        t = target(d),
+        m = (s.x + t.x) / 2;
+    return "M" + s.x + "," + s.y
+         + "C" + m   + "," + s.y
+         + " " + m   + "," + t.y
+         + " " + t.x + "," + t.y;
+  }
+
+  function diagonalY(d) {
+    var s = source(d),
+        t = target(d),
+        m = (s.y + t.y) / 2;
+    return "M" + s.x + "," + s.y
+         + "C" + s.x + "," + m
+         + " " + t.x + "," + m
+         + " " + t.x + "," + t.y;
+  }
+
+  var shapes = {
+    line:      line,
+    curve:     curve,
+    diagonal:  diagonalX,
+    diagonalX: diagonalX,
+    diagonalY: diagonalY
+  };
+  
+  function link(data) {
+    var path = shapes[shape];
+        
+    data.forEach(function(d) {
+      d[output.path] = path(d);
+    });
+    
+    return data;
+  }
+
+  link.shape = function(val) {
+    shape = val;
+    return link;
+  };
+
+  link.tension = function(val) {
+    tension = val;
+    return link;
+  };
+  
+  link.source = function(field) {
+    source = vg.accessor(field);
+    return link;
+  };
+  
+  link.target = function(field) {
+    target = vg.accessor(field);
+    return link;
+  };
+  
+  link.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return link;
+  };
+  
+  return link;
+};vg.data.pie = function() {
+  var one = function() { return 1; },
+      value = one,
+      start = 0,
+      end = 2 * Math.PI,
+      sort = false,
+      output = {
+        "startAngle": "startAngle",
+        "endAngle": "endAngle"
+      };
+
+  function pie(data) {
+    var values = data.map(function(d, i) { return +value(d); }),
+        a = start,
+        k = (end - start) / d3.sum(values),
+        index = d3.range(data.length);
+    
+    if (sort) {
+      index.sort(function(a, b) {
+        return values[a] - values[b];
+      });
+    }
+    
+    index.forEach(function(i) {
+      var d;
+      data[i].value = (d = values[i]);
+      data[i][output.startAngle] = a;
+      data[i][output.endAngle] = (a += d * k);
+    });
+    
+    return data;
+  }
+
+  pie.sort = function(b) {
+    sort = b;
+    return pie;
+  };
+       
+  pie.value = function(field) {
+    value = field ? vg.accessor(field) : one;
+    return pie;
+  };
+  
+  pie.startAngle = function(startAngle) {
+    start = Math.PI * startAngle / 180;
+    return pie;
+  };
+  
+  pie.endAngle = function(endAngle) {
+    end = Math.PI * endAngle / 180;
+    return pie;
+  };
+
+  pie.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return pie;
+  };
+
+  return pie;
+};vg.data.slice = function() {
+  var by = null,
+      field = vg.accessor("data");
+
+  function slice(data) {
+    data = vg.values(data);
+    
+    if (by === "min") {
+      data = [data[vg.minIndex(data, field)]];
+    } else if (by === "max") {
+      data = [data[vg.maxIndex(data, field)]];
+    } else if (by === "median") {
+      var list = data.slice().sort(function(a,b) {
+        a = field(a); b = field(b);
+        return a < b ? -1 : a > b ? 1 : 0;
+      });
+      data = [data[~~(list.length/2)]];
+    } else {
+      var idx = vg.array(by);
+      data = data.slice(idx[0], idx[1]);
+    }
+    return data;
+  }
+  
+  slice.by = function(x) {
+    by = x;
+    return slice;
+  };
+  
+  slice.field = function(f) {
+    field = vg.accessor(f);
+    return slice;
+  };
+
+  return slice;
+};vg.data.sort = function() {
+  var by = null;
+
+  function sort(data) {
+    data = (vg.isArray(data) ? data : data.values || []);
+    data.sort(by);
+    for (var i=0, n=data.length; i<n; ++i) data[i].index = i; // re-index
+    return data;
+  }
+  
+  sort.by = function(s) {
+    by = vg.comparator(s);
+    return sort;
+  };
+
+  return sort;
+};vg.data.stack = function() {
+  var layout = d3.layout.stack(),
+      point = vg.accessor("index"),
+      height = vg.accessor("data"),
+      params = ["offset", "order"],
+      output = {
+        "y0": "y2",
+        "y1": "y",
+        "cy": "cy"
+      };
+
+  function stack(data) {
+    var out_y0 = output["y0"],
+        out_y1 = output["y1"],
+        out_cy = output["cy"];
+    
+    var series = stacks(data);
+    if (series.length === 0) return data;
+    
+    layout.out(function(d, y0, y) {
+      if (d.datum) {
+        d.datum[out_y0] = y0;
+        d.datum[out_y1] = y + y0;
+        d.datum[out_cy] = y0 + y/2;
+      }
+    })(series);
+    
+    return data;
+  }
+  
+  function stacks(data) {
+    var values = vg.values(data),
+        points = [], series = [],
+        a, i, n, j, m, k, p, v, x;
+
+    // exit early if no data
+    if (values.length === 0) return series;
+
+    // collect and sort data points
+    for (i=0, n=values.length; i<n; ++i) {
+      a = vg.values(values[i]);
+      for (j=0, m=a.length; j<m; ++j) {
+        points.push({x:point(a[j]), y:height(a[j]), z:i, datum:a[j]});
+      }
+      series.push([]);
+    }
+    points.sort(function(a,b) {
+      return a.x<b.x ? -1 : a.x>b.x ? 1 : (a.z<b.z ? -1 : a.z>b.z ? 1 : 0);
+    });
+
+    // emit data series for stack layout
+    for (x=points[0].x, i=0, j=0, k=0, n=points.length; k<n; ++k) {
+      p = points[k];    
+      if (p.x !== x) {
+        while (i < series.length) series[i++].push({x:j, y:0});
+        x = p.x; i = 0; j += 1;
+      }
+      while (p.z > i) series[i++].push({x:j, y:0});
+      p.x = j;
+      series[i++].push(p);
+    }
+    while (i < series.length) series[i++].push({x:j, y:0});
+
+    return series;
+  }
+       
+  stack.point = function(field) {
+    point = vg.accessor(field);
+    return stack;
+  };
+  
+  stack.height = function(field) {
+    height = vg.accessor(field);
+    return stack;
+  };
+
+  params.forEach(function(name) {
+    stack[name] = function(x) {
+      layout[name](x);
+      return stack;
+    }
+  });
+
+  stack.output = function(map) {
+    d3.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return stack;
+  };
+
+  return stack;
+};vg.data.stats = function() {
+  var value = vg.accessor("data"),
+      assign = false,
+      median = false,
+      output = {
+        "count":    "count",
+        "min":      "min",
+        "max":      "max",
+        "sum":      "sum",
+        "mean":     "mean",
+        "variance": "variance",
+        "stdev":    "stdev",
+        "median":   "median"
+      };
+  
+  function reduce(data) {
+    var min = +Infinity,
+        max = -Infinity,
+        sum = 0,
+        mean = 0,
+        M2 = 0,
+        i, len, v, delta;
+
+    var list = (vg.isArray(data) ? data : data.values || []).map(value);
+    
+    // compute aggregates
+    for (i=0, len=list.length; i<len; ++i) {
+      v = list[i];
+      if (v < min) min = v;
+      if (v > max) max = v;
+      sum += v;
+      delta = v - mean;
+      mean = mean + delta / (i+1);
+      M2 = M2 + delta * (v - mean);
+    }
+    M2 = M2 / (len - 1);
+    
+    var o = vg.isArray(data) ? {} : data;
+    if (median) {
+      list.sort(vg.numcmp);
+      i = list.length >> 1;
+      o[output.median] = list.length % 2
+        ? list[i]
+        : (list[i-1] + list[i])/2;
+    }
+    o[output.count] = len;
+    o[output.min] = min;
+    o[output.max] = max;
+    o[output.sum] = sum;
+    o[output.mean] = mean;
+    o[output.variance] = M2;
+    o[output.stdev] = Math.sqrt(M2);
+    
+    if (assign) {
+      list = (vg.isArray(data) ? data : data.values);
+      v = {};
+      v[output.count] = len;
+      v[output.min] = min;
+      v[output.max] = max;
+      v[output.sum] = sum;
+      v[output.mean] = mean;
+      v[output.variance] = M2;
+      v[output.stdev] = Math.sqrt(M2);
+      if (median) v[output.median] = o[output.median];
+      for (i=0, len=list.length; i<len; ++i) {
+        list[i].stats = v;
+      }
+    }
+    
+    return o;
+  }
+  
+  function stats(data) {
+    return (vg.isArray(data) ? [data] : data.values || [])
+      .map(reduce); // no pun intended
+  }
+  
+  stats.median = function(bool) {
+    median = bool || false;
+    return stats;
+  };
+  
+  stats.value = function(field) {
+    value = vg.accessor(field);
+    return stats;
+  };
+
+  stats.assign = function(b) {
+    assign = b;
+    return stats;
+  };
+  
+  stats.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return stats;
+  };
+  
+  return stats;
+};vg.data.treemap = function() {
+  var layout = d3.layout.treemap()
+                 .children(function(d) { return d.values; }),
+      value = vg.accessor("data"),
+      size = ["width", "height"],
+      params = ["round", "sticky", "ratio", "padding"],
+      output = {
+        "x": "x",
+        "y": "y",
+        "dx": "width",
+        "dy": "height"
+      };
+
+  function treemap(data, db, group) {
+    data = layout
+      .size(vg.data.size(size, group))
+      .value(value)
+      .nodes(vg.isTree(data) ? data.nodes() : data);
+    
+    var keys = vg.keys(output),
+        len = keys.length;
+    data.forEach(function(d) {
+      var key, val;
+      for (var i=0; i<len; ++i) {
+        key = keys[i];
+        if (key !== output[key]) {
+          val = d[key];
+          delete d[key];
+          d[output[key]] = val;
+        }
+      }
+    });
+    
+    return data;
+  }
+
+  treemap.size = function(sz) {
+    size = sz;
+    return treemap;
+  };
+
+  treemap.value = function(field) {
+    value = vg.accessor(field);
+    return treemap;
+  };
+
+  params.forEach(function(name) {
+    treemap[name] = function(x) {
+      layout[name](x);
+      return treemap;
+    }
+  });
+
+  treemap.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return treemap;
+  };
+
+  return treemap;
+};vg.data.truncate = function() {
+  var value = vg.accessor("data"),
+      as = "truncate",
+      position = "right",
+      ellipsis = "...",
+      wordBreak = true,
+      limit = 100;
+  
+  var truncate = vg.data.mapper(function(d) {
+    var text = vg.truncate(value(d), limit, position, wordBreak, ellipsis);
+    return (d[as] = text, d);
+  });
+
+  truncate.value = function(field) {
+    value = vg.accessor(field);
+    return truncate;
+  };
+  
+  truncate.output = function(field) {
+    as = field;
+    return truncate;
+  };
+
+  truncate.limit = function(len) {
+    limit = +len;
+    return truncate;
+  };
+  
+  truncate.position = function(pos) {
+    position = pos;
+    return truncate;
+  };
+
+  truncate.ellipsis = function(str) {
+    ellipsis = str+"";
+    return truncate;
+  };
+
+  truncate.wordbreak = function(b) {
+    wordBreak = !!b;
+    return truncate;
+  };
+
+  return truncate;
+};vg.data.unique = function() {
+
+  var field = null,
+      as = "field";
+
+  function unique(data) {
+    return vg.unique(data, field)
+      .map(function(x) {
+        var o = {};
+        o[as] = x;
+        return o;
+      });
+  }
+  
+  unique.field = function(f) {
+    field = vg.accessor(f);
+    return unique;
+  };
+  
+  unique.as = function(x) {
+    as = x;
+    return unique;
+  };
+
+  return unique;
+};vg.data.window = function() {
+
+  var size = 2,
+      step = 1;
+  
+  function win(data) {
+    data = vg.isArray(data) ? data : data.values || [];
+    var runs = [], i, j, n=data.length-size, curr;
+    for (i=0; i<=n; i+=step) {
+      for (j=0, curr=[]; j<size; ++j) curr.push(data[i+j]);
+      runs.push({key: i, values: curr});
+    }
+    return {values: runs};
+  }
+  
+  win.size = function(n) {
+    size = n;
+    return win;
+  };
+  
+  win.step = function(n) {
+    step = n;
+    return win;
+  };
+
+  return win;
+};vg.data.wordcloud = function() {
+  var layout = d3.layout.cloud().size([900, 500]),
+      text = vg.accessor("data"),
+      size = ["width", "height"],
+      fontSize = function() { return 14; },
+      rotate = function() { return 0; },
+      params = ["font", "fontStyle", "fontWeight", "padding"];
+  
+  var output = {
+    "x": "x",
+    "y": "y",
+    "size": "fontSize",
+    "font": "font",
+    "rotate": "angle"
+  };
+  
+  function cloud(data, db, group) {
+    function finish(tags, bounds) {
+      var size = layout.size(),
+          dx = size[0] / 2,
+          dy = size[1] / 2,
+          keys = vg.keys(output),
+          key, d, i, n, k, m = keys.length;
+
+      // sort data to match wordcloud order
+      data.sort(function(a,b) {
+        return fontSize(b) - fontSize(a);
+      });
+
+      for (i=0, n=tags.length; i<n; ++i) {
+        d = data[i];
+        for (k=0; k<m; ++k) {
+          key = keys[k];
+          d[output[key]] = tags[i][key];
+          if (key === "x") d[output.x] += dx;
+          if (key === "y") d[output.y] += dy;
+        }
+      }
+    }
+    
+    layout
+      .size(vg.data.size(size, group))
+      .text(text)
+      .fontSize(fontSize)
+      .rotate(rotate)
+      .words(data)
+      .on("end", finish)
+      .start();
+    return data;
+  }
+
+  cloud.text = function(field) {
+    text = vg.accessor(field);
+    return cloud;
+  };
+  
+  cloud.size = function(sz) {
+    size = sz;
+    return cloud;
+  };
+         
+  cloud.fontSize = function(field) {
+    fontSize = vg.accessor(field);
+    return cloud;
+  };
+  
+  cloud.rotate = function(x) {
+    var v;
+    if (vg.isObject(x) && !Array.isArray(x)) {
+      if (x.random !== undefined) {
+        v = (v = x.random) ? vg.array(v) : [0];
+        rotate = function() {
+          return v[~~(Math.random()*v.length-0.00001)];
+        };
+      } else if (x.alternate !== undefined) {
+        v = (v = x.alternate) ? vg.array(v) : [0];
+        rotate = function(d, i) {
+          return v[i % v.length];
+        };
+      }
+    } else {
+      rotate = vg.accessor(field);
+    }
+    return cloud;
+  };
+
+  params.forEach(function(name) {
+    cloud[name] = function(x) {
+      layout[name](x);
+      return cloud;
+    }
+  });
+
+  cloud.output = function(map) {
+    vg.keys(output).forEach(function(k) {
+      if (map[k] !== undefined) {
+        output[k] = map[k];
+      }
+    });
+    return cloud;
+  };
+  
+  return cloud;
+};vg.data.zip = function() {
+  var z = null,
+      as = "zip",
+      key = vg.accessor("data"),
+      defaultValue = undefined,
+      withKey = null;
+
+  function zip(data, db) {
+    var zdata = db[z], zlen = zdata.length, v, d, i, len, map;
+    
+    if (withKey) {
+      map = {};
+      zdata.forEach(function(s) { map[withKey(s)] = s; });
+    }
+    
+    for (i=0, len=data.length; i<len; ++i) {
+      d = data[i];
+      d[as] = map
+        ? ((v=map[key(d)]) != null ? v : defaultValue)
+        : zdata[i % zlen];
+    }
+    
+    return data;
+  }
+
+  zip["with"] = function(d) {
+    z = d;
+    return zip;
+  };
+  
+  zip["default"] = function(d) {
+    defaultValue = d;
+    return zip;
+  };
+
+  zip.as = function(name) {
+    as = name;
+    return zip;
+  };
+
+  zip.key = function(k) {
+    key = vg.accessor(k);
+    return zip;
+  };
+
+  zip.withKey = function(k) {
+    withKey = vg.accessor(k);
+    return zip;
+  };
+
+  return zip;
+};vg.parse = {};vg.parse.axes = (function() {
+  var ORIENT = {
+    "x":      "bottom",
+    "y":      "left",
+    "top":    "top",
+    "bottom": "bottom",
+    "left":   "left",
+    "right":  "right"
+  };
+
+  function axes(spec, axes, scales) {
+    (spec || []).forEach(function(def, index) {
+      axes[index] = axes[index] || vg.scene.axis();
+      axis(def, index, axes[index], scales);
+    });
+  };
+
+  function axis(def, index, axis, scales) {
+    // axis scale
+    if (def.scale !== undefined) {
+      axis.scale(scales[def.scale]);
+    }
+
+    // axis orientation
+    axis.orient(def.orient || ORIENT[def.type]);
+    // axis offset
+    axis.offset(def.offset || 0);
+    // axis layer
+    axis.layer(def.layer || "front");
+    // axis grid lines
+    axis.grid(def.grid || false);
+    // axis title
+    axis.title(def.title || null);
+    // axis title offset
+    axis.titleOffset(def.titleOffset != null
+      ? def.titleOffset : vg.config.axis.titleOffset);
+    // axis values
+    axis.tickValues(def.values || null);
+    // axis label formatting
+    axis.tickFormat(def.format ? d3.format(def.format) : null);
+    // axis tick subdivision
+    axis.tickSubdivide(def.subdivide || 0);
+    // axis tick padding
+    axis.tickPadding(def.tickPadding || vg.config.axis.padding);
+
+    // axis tick size(s)
+    var size = [];
+    if (def.tickSize !== undefined) {
+      for (var i=0; i<3; ++i) size.push(def.tickSize);
+    } else {
+      var ts = vg.config.axis.tickSize;
+      size = [ts, ts, ts];
+    }
+    if (def.tickSizeMajor != null) size[0] = def.tickSizeMajor;
+    if (def.tickSizeMinor != null) size[1] = def.tickSizeMinor;
+    if (def.tickSizeEnd   != null) size[2] = def.tickSizeEnd;
+    if (size.length) {
+      axis.tickSize.apply(axis, size);
+    }
+
+    // tick arguments
+    if (def.ticks != null) {
+      var ticks = vg.isArray(def.ticks) ? def.ticks : [def.ticks];
+      axis.ticks.apply(axis, ticks);
+    } else {
+      axis.ticks(vg.config.axis.ticks);
+    }
+    
+    // style properties
+    var p = def.properties;
+    if (p && p.ticks) {
+      axis.majorTickProperties(p.majorTicks
+        ? vg.extend({}, p.ticks, p.majorTicks) : p.ticks);
+      axis.minorTickProperties(p.minorTicks
+        ? vg.extend({}, p.ticks, p.minorTicks) : p.ticks);
+    } else {
+      axis.majorTickProperties(p && p.majorTicks || {});
+      axis.minorTickProperties(p && p.minorTicks || {});
+    }
+    axis.tickLabelProperties(p && p.labels || {});
+    axis.titleProperties(p && p.title || {});
+    axis.gridLineProperties(p && p.grid || {});
+    axis.domainProperties(p && p.axis || {});
+  }
+  
+  return axes;
+})();vg.parse.data = function(spec, callback) {
+  var model = {
+    defs: spec,
+    load: {},
+    flow: {},
+    source: {}
+  };
+
+  var count = 0;
+  
+  function load(d) {
+    return function(error, data) {
+      if (error) {
+        vg.error("LOADING FAILED: " + d.url);
+      } else {
+        model.load[d.name] = vg.data.read(data.toString(), d.format);
+      }
+      if (--count === 0) callback();
+    }
+  }
+  
+  (spec || []).forEach(function(d) {
+    if (d.url) {
+      count += 1;
+      vg.data.load(d.url, load(d)); 
+    }
+     
+    if (d.values) {
+      if (d.format && d.format.parse) {
+        // run specified value parsers
+        vg.data.read.parse(d.values, d.format.parse);
+      }
+      model.load[d.name] = d.values;
+    }
+    
+    if (d.source) {
+      var list = model.source[d.source] || (model.source[d.source] = []);
+      list.push(d.name);
+    }
+    
+    if (d.transform) {
+      model.flow[d.name] = vg.parse.dataflow(d);
+    }
+  });
+  
+  if (count === 0) setTimeout(callback, 1);
+  return model;
+};vg.parse.dataflow = function(def) {
+  var tx = (def.transform || []).map(vg.parse.transform);
+  return !tx.length ? vg.identity :
+    function(data, db, group) {
+      return tx.reduce(function(d,t) { return t(d, db, group); }, data);
+    };
+};vg.parse.expr = (function() {
+  
+  var CONSTANT = {
+  	"E":       "Math.E",
+  	"LN2":     "Math.LN2",
+  	"LN10":    "Math.LN10",
+  	"LOG2E":   "Math.LOG2E",
+  	"LOG10E":  "Math.LOG10E",
+  	"PI":      "Math.PI",
+  	"SQRT1_2": "Math.SQRT1_2",
+  	"SQRT2":   "Math.SQRT2"
+  };
+
+  var FUNCTION = {
+  	"abs":    "Math.abs",
+  	"acos":   "Math.acos",
+  	"asin":   "Math.asin",
+  	"atan":   "Math.atan",
+  	"atan2":  "Math.atan2",
+  	"ceil":   "Math.ceil",
+  	"cos":    "Math.cos",
+  	"exp":    "Math.exp",
+  	"floor":  "Math.floor",
+  	"log":    "Math.log",
+  	"max":    "Math.max",
+  	"min":    "Math.min",
+  	"pow":    "Math.pow",
+  	"random": "Math.random",
+  	"round":  "Math.round",
+  	"sin":    "Math.sin",
+  	"sqrt":   "Math.sqrt",
+  	"tan":    "Math.tan"
+  };
+  
+  var lexer = /([\"\']|[\=\<\>\~\&\|\?\:\+\-\/\*\%\!\^\,\;\[\]\{\}\(\) ]+)/;
+      
+  return function(x) {
+    var tokens = x.split(lexer),
+        t, v, i, n, sq, dq;
+
+    for (sq=0, dq=0, i=0, n=tokens.length; i<n; ++i) {
+      var t = tokens[i];
+      if (t==="'") { if (!dq) sq = !sq; continue; }
+      if (t==='"') { if (!sq) dq = !dq; continue; }
+      if (dq || sq) continue;
+      if (CONSTANT[t]) {
+        tokens[i] = CONSTANT[t];
+      }
+      if (FUNCTION[t] && (v=tokens[i+1]) && v[0]==="(") {
+        tokens[i] = FUNCTION[t];
+      }
+    }
+    
+    return Function("d", "index", "data", "return ("+tokens.join("")+");");
+  };
+  
+})();vg.parse.legends = (function() {
+
+  function legends(spec, legends, scales) {
+    (spec || []).forEach(function(def, index) {
+      legends[index] = legends[index] || vg.scene.legend();
+      legend(def, index, legends[index], scales);
+    });
+  };
+
+  function legend(def, index, legend, scales) {
+    // legend scales
+    legend.size  (def.size   ? scales[def.size]   : null);
+    legend.shape (def.shape  ? scales[def.shape]  : null);
+    legend.fill  (def.fill   ? scales[def.fill]   : null);
+    legend.stroke(def.stroke ? scales[def.stroke] : null);
+
+    // legend orientation
+    if (def.orient) legend.orient(def.orient);
+
+    // legend offset
+    if (def.offset != null) legend.offset(def.offset);
+
+    // legend title
+    legend.title(def.title || null);
+
+    // legend values
+    legend.values(def.values || null);
+
+    // legend label formatting
+    legend.format(def.format !== undefined ? d3.format(def.format) : null);
+
+    // style properties
+    var p = def.properties;
+    legend.titleProperties(p && p.title || {});
+    legend.labelProperties(p && p.labels || {});
+    legend.legendProperties(p && p.legend || {});
+    legend.symbolProperties(p && p.symbols || {});
+    legend.gradientProperties(p && p.gradient || {});
+  }
+  
+  return legends;
+})();vg.parse.mark = function(mark) {
+  var props = mark.properties,
+      group = mark.marks;
+  
+  // parse mark property definitions
+  vg.keys(props).forEach(function(k) {
+    props[k] = vg.parse.properties(mark.type, props[k]);
+  });
+  // parse delay function
+  if (mark.delay) {
+    mark.delay = vg.parse.properties(mark.type, {delay: mark.delay});
+  }
+      
+  // parse mark data definition
+  if (mark.from) {
+    var name = mark.from.data,
+        tx = vg.parse.dataflow(mark.from);
+    mark.from = function(db, group, parentData) {
+      var data = vg.scene.data(name ? db[name] : null, parentData);
+      return tx(data, db, group);
+    };
+  }
+  
+  // recurse if group type
+  if (group) {
+    mark.marks = group.map(vg.parse.mark);
+  }
+      
+  return mark;
+};vg.parse.marks = function(spec, width, height) {
+  return {
+    type: "group",
+    width: width,
+    height: height,
+    scales: spec.scales || [],
+    axes: spec.axes || [],
+    legends: spec.legends || [],
+    marks: (spec.marks || []).map(vg.parse.mark)
+  };
+};vg.parse.padding = function(pad) {
+  if (pad == null) return "auto";
+  else if (vg.isString(pad)) return pad==="strict" ? "strict" : "auto";
+  else if (vg.isObject(pad)) return pad;
+  var p = vg.isNumber(pad) ? pad : 20;
+  return {top:p, left:p, right:p, bottom:p};
+};
+vg.parse.properties = (function() {
+  function compile(mark, spec) {
+    var code = "",
+        names = vg.keys(spec),
+        i, len, name, ref, vars = {};
+        
+    code += "var o = trans ? {} : item;\n"
+    
+    for (i=0, len=names.length; i<len; ++i) {
+      ref = spec[name = names[i]];
+      code += (i > 0) ? "\n  " : "  ";
+      code += "o."+name+" = "+valueRef(name, ref)+";";
+      vars[name] = true;
+    }
+    
+    if (vars.x2) {
+      if (vars.x) {
+        code += "\n  if (o.x > o.x2) { "
+              + "var t = o.x; o.x = o.x2; o.x2 = t; };";
+        code += "\n  o.width = (o.x2 - o.x);";
+      } else if (vars.width && !vars.x1) {
+        code += "\n  o.x = (o.x2 - o.width);";
+      } 
+    }
+
+    if (vars.y2) {
+      if (vars.y) {
+        code += "\n  if (o.y > o.y2) { "
+              + "var t = o.y; o.y = o.y2; o.y2 = t; };";
+        code += "\n  o.height = (o.y2 - o.y);";
+      } else if (vars.height && !vars.y1) {
+        code += "\n  o.y = (o.y2 - o.height);";
+      }
+    }
+    
+    if (hasPath(mark, vars)) {
+      code += "\n  if (o['path:parsed']) o['path:parsed'] = null;"
+    }
+    code += "\n  if (trans) trans.interpolate(item, o);";
+
+    try {
+      return Function("item", "group", "trans", code);
+    } catch (e) {
+      vg.error(e);
+      vg.log(code);
+    }
+  }
+  
+  function hasPath(mark, vars) {
+    return vars.path ||
+      ((mark==="area" || mark==="line") &&
+        (vars.x || vars.x2 || vars.width ||
+         vars.y || vars.y2 || vars.height ||
+         vars.tension || vars.interpolate));
+  }
+  
+  var GROUP_VARS = {
+    "width": 1,
+    "height": 1,
+    "mark.group.width": 1,
+    "mark.group.height": 1
+  };
+
+  function valueRef(name, ref) {
+    if (ref == null) return null;
+    var isColor = name==="fill" || name==="stroke";
+
+    if (isColor) {
+      if (ref.c) {
+        return colorRef("hcl", ref.h, ref.c, ref.l);
+      } else if (ref.h || ref.s) {
+        return colorRef("hsl", ref.h, ref.s, ref.l);
+      } else if (ref.l || ref.a) {
+        return colorRef("lab", ref.l, ref.a, ref.b);
+      } else if (ref.r || ref.g || ref.b) {
+        return colorRef("rgb", ref.r, ref.g, ref.b);
+      }
+    }
+
+    // initialize value
+    var val = "item.datum.data";
+    if (ref.value !== undefined) {
+      val = vg.str(ref.value);
+    }
+
+    // get field reference for enclosing group
+    if (ref.group != null) {
+      var grp = "";
+      if (vg.isString(ref.group)) {
+        grp = GROUP_VARS[ref.group]
+          ? "group." + ref.group
+          : "group.datum["+vg.field(ref.group).map(vg.str).join("][")+"]";
+      }
+    }
+
+    // get data field value
+    if (ref.field != null) {
+      if (vg.isString(ref.field)) {
+        val = "item.datum["+vg.field(ref.field).map(vg.str).join("][")+"]";
+        if (ref.group != null) { val = grp+"["+val+"]"; }
+      } else {
+        val = "this.accessor(group.datum["
+            + vg.field(ref.field.group).map(vg.str).join("][")
+            + "])(item.datum.data)";
+      }
+    } else if (ref.group != null) {
+      val = grp;
+    }
+
+    // run through scale function
+    if (ref.scale != null) {
+      var scale = vg.isString(ref.scale)
+        ? vg.str(ref.scale)
+        : (ref.scale.group ? "group" : "item")
+          + ".datum[" + vg.str(ref.scale.group || ref.scale.field) + "]";
+      scale = "group.scales[" + scale + "]";
+      val = scale + (ref.band ? ".rangeBand()" : "("+val+")");
+    }
+    
+    // multiply, offset, return value
+    val = "(" + (ref.mult?(vg.number(ref.mult)+" * "):"") + val + ")"
+      + (ref.offset ? " + " + vg.number(ref.offset) : "");
+    if (isColor) val = '('+val+')+""';
+    return val;
+  }
+  
+  function colorRef(type, x, y, z) {
+    var xx = x ? valueRef("", x) : vg.config.color[type][0],
+        yy = y ? valueRef("", y) : vg.config.color[type][1],
+        zz = z ? valueRef("", z) : vg.config.color[type][2];
+    return "(this.d3." + type + "(" + [xx,yy,zz].join(",") + ') + "")';
+  }
+  
+  return compile;
+})();vg.parse.scales = (function() {
+  var LINEAR = "linear",
+      ORDINAL = "ordinal",
+      LOG = "log",
+      POWER = "pow",
+      TIME = "time",
+      GROUP_PROPERTY = {width: 1, height: 1};
+
+  function scales(spec, scales, db, group) {
+    return (spec || []).reduce(function(o, def) {
+      var name = def.name, prev = name + ":prev";
+      o[name] = scale(def, o[name], db, group);
+      o[prev] = o[prev] || o[name];
+      return o;
+    }, scales || {});
+  }
+
+  function scale(def, scale, db, group) {
+    var s = instance(def, scale),
+        m = s.type===ORDINAL ? ordinal : quantitative,
+        rng = range(def, group),
+        data = vg.values(group.datum);
+
+    m(def, s, rng, db, data);
+    return s;
+  }
+
+  function instance(def, scale) {
+    var type = def.type || LINEAR;
+    if (!scale || type !== scale.type) {
+      var ctor = vg.config.scale[type] || d3.scale[type];
+      if (!ctor) vg.error("Unrecognized scale type: " + type);
+      (scale = ctor()).type = scale.type || type;
+      scale.scaleName = def.name;
+    }
+    return scale;
+  }
+
+  function ordinal(def, scale, rng, db, data) {
+    var domain, refs, values, str;
+    
+    // domain
+    domain = def.domain;
+    if (vg.isArray(domain)) {
+      scale.domain(domain);
+    } else if (vg.isObject(domain)) {
+      refs = def.domain.fields || vg.array(def.domain);
+      values = refs.reduce(function(values, r) {        
+        var dat = vg.values(db[r.data] || data),
+            get = vg.accessor(vg.isString(r.field)
+              ? r.field : "data." + vg.accessor(r.field.group)(data));
+        return vg.unique(dat, get, values);
+      }, []);
+      if (def.sort) values.sort(vg.cmp);
+      scale.domain(values);
+    }
+
+    // range
+    str = typeof rng[0] === 'string';
+    if (str || rng.length > 2) {
+      scale.range(rng); // color or shape values
+    } else if (def.points) {
+      scale.rangePoints(rng, def.padding||0);
+    } else if (def.round || def.round===undefined) {
+      scale.rangeRoundBands(rng, def.padding||0);
+    } else {
+      scale.rangeBands(rng, def.padding||0);
+    }
+  }
+
+  function quantitative(def, scale, rng, db, data) {
+    var domain, refs, interval, z;
+
+    // domain
+    domain = [null, null];
+    function extract(ref, min, max, z) {
+      var dat = vg.values(db[ref.data] || data);
+      var fields = vg.array(ref.field).map(function(f) {
+        return vg.isString(f) ? f
+          : "data." + vg.accessor(f.group)(data);
+      });
+      
+      fields.forEach(function(f,i) {
+        f = vg.accessor(f);
+        if (min) domain[0] = d3.min([domain[0], d3.min(dat, f)]);
+        if (max) domain[z] = d3.max([domain[z], d3.max(dat, f)]);
+      });
+    }
+    if (def.domain !== undefined) {
+      if (vg.isArray(def.domain)) {
+        domain = def.domain.slice();
+      } else if (vg.isObject(def.domain)) {
+        refs = def.domain.fields || vg.array(def.domain);
+        refs.forEach(function(r) { extract(r,1,1,1); });
+      } else {
+        domain = def.domain;
+      }
+    }
+    z = domain.length - 1;
+    if (def.domainMin !== undefined) {
+      if (vg.isObject(def.domainMin)) {
+        domain[0] = null;
+        refs = def.domainMin.fields || vg.array(def.domainMin);
+        refs.forEach(function(r) { extract(r,1,0,z); });
+      } else {
+        domain[0] = def.domainMin;
+      }
+    }
+    if (def.domainMax !== undefined) {
+      if (vg.isObject(def.domainMax)) {
+        domain[z] = null;
+        refs = def.domainMax.fields || vg.array(def.domainMax);
+        refs.forEach(function(r) { extract(r,0,1,z); });
+      } else {
+        domain[z] = def.domainMax;
+      }
+    }
+    if (def.type !== LOG && def.type !== TIME && (def.zero || def.zero===undefined)) {
+      domain[0] = Math.min(0, domain[0]);
+      domain[z] = Math.max(0, domain[z]);
+    }
+    scale.domain(domain);
+
+    // range
+    // vertical scales should flip by default, so use XOR here
+    if (def.range === "height") rng = rng.reverse();
+    scale[def.round && scale.rangeRound ? "rangeRound" : "range"](rng);
+
+    if (def.exponent && def.type===POWER) scale.exponent(def.exponent);
+    if (def.clamp) scale.clamp(true);
+    if (def.nice) {
+      if (def.type === TIME) {
+        interval = d3.time[def.nice];
+        if (!interval) vg.error("Unrecognized interval: " + interval);
+        scale.nice(interval);
+      } else {
+        scale.nice();
+      }
+    }
+  }
+
+  function range(def, group) {
+    var rng = [null, null];
+
+    if (def.range !== undefined) {
+      if (typeof def.range === 'string') {
+        if (GROUP_PROPERTY[def.range]) {
+          rng = [0, group[def.range]];
+        } else if (vg.config.range[def.range]) {
+          rng = vg.config.range[def.range];
+        } else {
+          vg.error("Unrecogized range: "+def.range);
+          return rng;
+        }
+      } else if (vg.isArray(def.range)) {
+        rng = def.range;
+      } else {
+        rng = [0, def.range];
+      }
+    }
+    if (def.rangeMin !== undefined) {
+      rng[0] = def.rangeMin;
+    }
+    if (def.rangeMax !== undefined) {
+      rng[rng.length-1] = def.rangeMax;
+    }
+    
+    if (def.reverse !== undefined) {
+      var rev = def.reverse;
+      if (vg.isObject(rev)) {
+        rev = vg.accessor(rev.field)(group.datum);
+      }
+      if (rev) rng = rng.reverse();
+    }
+    
+    return rng;
+  }
+
+  return scales;
+})();
+vg.parse.spec = function(spec, callback, viewFactory) {
+  
+  viewFactory = viewFactory || vg.ViewFactory;
+  
+  function parse(spec) {
+    // protect against subsequent spec modification
+    spec = vg.duplicate(spec);
+    
+    var width = spec.width || 500,
+        height = spec.height || 500,
+        viewport = spec.viewport || null;
+    
+    var defs = {
+      width: width,
+      height: height,
+      viewport: viewport,
+      padding: vg.parse.padding(spec.padding),
+      marks: vg.parse.marks(spec, width, height),
+      data: vg.parse.data(spec.data, function() { callback(viewConstructor); })
+    };
+    
+    var viewConstructor = viewFactory(defs);
+  }
+  
+  vg.isObject(spec) ? parse(spec) :
+    d3.json(spec, function(error, json) {
+      error ? vg.error(error) : parse(json);
+    });
+};vg.parse.transform = function(def) {
+  var tx = vg.data[def.type]();
+      
+  vg.keys(def).forEach(function(k) {
+    if (k === 'type') return;
+    (tx[k])(def[k]);
+  });
+  
+  return tx;
+};vg.scene = {};
+
+vg.scene.GROUP  = "group",
+vg.scene.ENTER  = 0,
+vg.scene.UPDATE = 1,
+vg.scene.EXIT   = 2;
+
+vg.scene.DEFAULT_DATA = {"sentinel":1}
+
+vg.scene.data = function(data, parentData) {
+  var DEFAULT = vg.scene.DEFAULT_DATA;
+
+  // if data is undefined, inherit or use default
+  data = vg.values(data || parentData || [DEFAULT]);
+
+  // if inheriting default data, ensure its in an array
+  if (data === DEFAULT) data = [DEFAULT];
+  
+  return data;
+};
+
+vg.scene.fontString = function(o) {
+  return (o.fontStyle ? o.fontStyle + " " : "")
+    + (o.fontVariant ? o.fontVariant + " " : "")
+    + (o.fontWeight ? o.fontWeight + " " : "")
+    + (o.fontSize != null ? o.fontSize : vg.config.render.fontSize) + "px "
+    + (o.font || vg.config.render.font);
+};vg.scene.Item = (function() {
+  function item(mark) {
+    this.mark = mark;
+  }
+  
+  var prototype = item.prototype;
+
+  prototype.hasPropertySet = function(name) {
+    var props = this.mark.def.properties;
+    return props && props[name] != null;
+  };
+
+  prototype.cousin = function(offset, index) {
+    if (offset === 0) return this;
+    offset = offset || -1;
+    var mark = this.mark,
+        group = mark.group,
+        iidx = index==null ? mark.items.indexOf(this) : index,
+        midx = group.items.indexOf(mark) + offset;
+    return group.items[midx].items[iidx];
+  };
+  
+  prototype.sibling = function(offset) {
+    if (offset === 0) return this;
+    offset = offset || -1;
+    var mark = this.mark,
+        iidx = mark.items.indexOf(this) + offset;
+    return mark.items[iidx];
+  };
+  
+  prototype.remove = function() {
+    var item = this,
+        list = item.mark.items,
+        i = list.indexOf(item);
+    if (i >= 0) (i===list.length-1) ? list.pop() : list.splice(i, 1);
+    return item;
+  };
+  
+  return item;
+})();
+
+vg.scene.item = function(mark) {
+  return new vg.scene.Item(mark);
+};vg.scene.visit = function(node, func) {
+  var i, n, items;
+  if (func(node)) return true;
+  if (items = node.items) {
+    for (i=0, n=items.length; i<n; ++i) {
+      if (vg.scene.visit(items[i], func)) return true;
+    }
+  }
+};vg.scene.build = (function() {
+  var GROUP  = vg.scene.GROUP,
+      ENTER  = vg.scene.ENTER,
+      UPDATE = vg.scene.UPDATE,
+      EXIT   = vg.scene.EXIT,
+      DEFAULT= {"sentinel":1};
+  
+  function build(def, db, node, parentData) {
+    var data = vg.scene.data(
+      def.from ? def.from(db, node, parentData) : null,
+      parentData);
+    
+    // build node and items
+    node = buildNode(def, node);
+    node.items = buildItems(def, data, node);
+    buildTrans(def, node);
+    
+    // recurse if group
+    if (def.type === GROUP) {
+      buildGroup(def, db, node);
+    }
+    
+    return node;
+  };
+  
+  function buildNode(def, node) {
+    node = node || {};
+    node.def = def;
+    node.marktype = def.type;
+    node.interactive = !(def.interactive === false);
+    return node;
+  }
+  
+  function buildItems(def, data, node) {
+    var keyf = keyFunction(def.key),
+        prev = node.items || [],
+        next = [],
+        map = {},
+        i, key, len, item, datum, enter;
+
+    for (i=0, len=prev.length; i<len; ++i) {
+      item = prev[i];
+      item.status = EXIT;
+      if (keyf) map[item.key] = item;
+    }
+    
+    for (i=0, len=data.length; i<len; ++i) {
+      datum = data[i];
+      key = i;
+      item = keyf ? map[key = keyf(datum)] : prev[i];
+      enter = item ? false : (item = vg.scene.item(node), true);
+      item.status = enter ? ENTER : UPDATE;
+      item.datum = datum;
+      item.key = key;
+      next.push(item);
+    }
+
+    for (i=0, len=prev.length; i<len; ++i) {
+      item = prev[i];
+      if (item.status === EXIT) {
+        item.key = keyf ? item.key : next.length;
+        next.push(item);
+      }
+    }
+    
+    return next;
+  }
+  
+  function buildGroup(def, db, node) {
+    var groups = node.items,
+        marks = def.marks,
+        i, len, m, mlen, name, group;
+
+    for (i=0, len=groups.length; i<len; ++i) {
+      group = groups[i];
+      
+      // update scales
+      if (group.scales) for (name in group.scales) {
+        if (name.indexOf(":prev") < 0) {
+          group.scales[name+":prev"] = group.scales[name].copy();
+        }
+      }
+
+      // build items
+      group.items = group.items || [];
+      for (m=0, mlen=marks.length; m<mlen; ++m) {
+        group.items[m] = build(marks[m], db, group.items[m], group.datum);
+        group.items[m].group = group;
+      }
+    }
+  }
+
+  function buildTrans(def, node) {
+    if (def.duration) node.duration = def.duration;
+    if (def.ease) node.ease = d3.ease(def.ease)
+    if (def.delay) {
+      var items = node.items, group = node.group, n = items.length, i;
+      for (i=0; i<n; ++i) def.delay.call(this, items[i], group);
+    }
+  }
+  
+  function keyFunction(key) {
+    if (key == null) return null;
+    var f = vg.array(key).map(vg.accessor);
+    return function(d) {
+      for (var s="", i=0, n=f.length; i<n; ++i) {
+        if (i>0) s += "|";
+        s += String(f[i](d));
+      }
+      return s;
+    }
+  }
+  
+  return build;
+})();vg.scene.bounds = (function() {
+
+  var parse = vg.canvas.path.parse,
+      boundPath = vg.canvas.path.bounds,
+      areaPath = vg.canvas.path.area,
+      linePath = vg.canvas.path.line,
+      halfpi = Math.PI / 2,
+      sqrt3 = Math.sqrt(3),
+      tan30 = Math.tan(30 * Math.PI / 180),
+      gfx = null;
+
+  function context() {
+    return gfx || (gfx = (vg.config.isNode
+      ? new (require("canvas"))(1,1)
+      : d3.select("body").append("canvas")
+          .attr("class", "vega_hidden")
+          .attr("width", 1)
+          .attr("height", 1)
+          .style("display", "none")
+          .node())
+      .getContext("2d"));
+  }
+
+  function pathBounds(o, path, bounds) {
+    if (path == null) {
+      bounds.set(0, 0, 0, 0);
+    } else {
+      boundPath(path, bounds);
+      if (o.stroke && o.opacity !== 0 && o.strokeWidth > 0) {
+        bounds.expand(o.strokeWidth);
+      }
+    }
+    return bounds;
+  }
+
+  function path(o, bounds) {
+    var p = o.path
+      ? o["path:parsed"] || (o["path:parsed"] = parse(o.path))
+      : null;
+    return pathBounds(o, p, bounds);
+  }
+  
+  function area(o, bounds) {
+    var items = o.mark.items, o = items[0];
+    var p = o["path:parsed"] || (o["path:parsed"]=parse(areaPath(items)));
+    return pathBounds(items[0], p, bounds);
+  }
+
+  function line(o, bounds) {
+    var items = o.mark.items, o = items[0];
+    var p = o["path:parsed"] || (o["path:parsed"]=parse(linePath(items)));
+    return pathBounds(items[0], p, bounds);
+  }
+
+  function rect(o, bounds) {
+    var x = o.x || 0,
+        y = o.y || 0,
+        w = (x + o.width) || 0,
+        h = (y + o.height) || 0;
+    bounds.set(x, y, w, h);
+    if (o.stroke && o.opacity !== 0 && o.strokeWidth > 0) {
+      bounds.expand(o.strokeWidth);
+    }
+    return bounds;
+  }
+
+  function image(o, bounds) {
+    var w = o.width || 0,
+        h = o.height || 0,
+        x = (o.x||0) - (o.align === "center"
+            ? w/2 : (o.align === "right" ? w : 0)),
+        y = (o.y||0) - (o.baseline === "middle"
+            ? h/2 : (o.baseline === "bottom" ? h : 0));
+    return bounds.set(x, y, x+w, y+h);
+  }
+
+  function rule(o, bounds) {
+    var x1, y1;
+    bounds.set(
+      x1 = o.x || 0,
+      y1 = o.y || 0,
+      o.x2 != null ? o.x2 : x1,
+      o.y2 != null ? o.y2 : y1
+    );
+    if (o.stroke && o.opacity !== 0 && o.strokeWidth > 0) {
+      bounds.expand(o.strokeWidth);
+    }
+    return bounds;
+  }
+  
+  function arc(o, bounds) {
+    var cx = o.x || 0,
+        cy = o.y || 0,
+        ir = o.innerRadius || 0,
+        or = o.outerRadius || 0,
+        sa = (o.startAngle || 0) - halfpi,
+        ea = (o.endAngle || 0) - halfpi,
+        xmin = Infinity, xmax = -Infinity,
+        ymin = Infinity, ymax = -Infinity,
+        a, i, n, x, y, ix, iy, ox, oy;
+
+    var angles = [sa, ea],
+        s = sa - (sa%halfpi);
+    for (i=0; i<4 && s<ea; ++i, s+=halfpi) {
+      angles.push(s);
+    }
+
+    for (i=0, n=angles.length; i<n; ++i) {
+      a = angles[i];
+      x = Math.cos(a); ix = ir*x; ox = or*x;
+      y = Math.sin(a); iy = ir*y; oy = or*y;
+      xmin = Math.min(xmin, ix, ox);
+      xmax = Math.max(xmax, ix, ox);
+      ymin = Math.min(ymin, iy, oy);
+      ymax = Math.max(ymax, iy, oy);
+    }
+
+    bounds.set(cx+xmin, cy+ymin, cx+xmax, cy+ymax);
+    if (o.stroke && o.opacity !== 0 && o.strokeWidth > 0) {
+      bounds.expand(o.strokeWidth);
+    }
+    return bounds;
+  }
+
+  function symbol(o, bounds) {
+    var size = o.size != null ? o.size : 100,
+        x = o.x || 0,
+        y = o.y || 0,
+        r, t, rx, ry;
+
+    switch (o.shape) {
+      case "cross":
+        r = Math.sqrt(size / 5) / 2;
+        t = 3*r;
+        bounds.set(x-t, y-t, x+y, y+t);
+        break;
+
+      case "diamond":
+        ry = Math.sqrt(size / (2 * tan30));
+        rx = ry * tan30;
+        bounds.set(x-rx, y-ry, x+rx, y+ry);
+        break;
+
+      case "square":
+        t = Math.sqrt(size);
+        r = t / 2;
+        bounds.set(x-r, y-r, x+r, y+r);
+        break;
+
+      case "triangle-down":
+        rx = Math.sqrt(size / sqrt3);
+        ry = rx * sqrt3 / 2;
+        bounds.set(x-rx, y-ry, x+rx, y+ry);
+        break;
+
+      case "triangle-up":
+        rx = Math.sqrt(size / sqrt3);
+        ry = rx * sqrt3 / 2;
+        bounds.set(x-rx, y-ry, x+rx, y+ry);
+        break;
+
+      default:
+        r = Math.sqrt(size/Math.PI);
+        bounds.set(x-r, y-r, x+r, y+r);
+    }
+    if (o.stroke && o.opacity !== 0 && o.strokeWidth > 0) {
+      bounds.expand(o.strokeWidth);
+    }
+    return bounds;
+  }
+
+  function text(o, bounds, noRotate) {
+    var x = (o.x || 0) + (o.dx || 0),
+        y = (o.y || 0) + (o.dy || 0),
+        h = o.fontSize || vg.config.render.fontSize,
+        a = o.align,
+        b = o.baseline,
+        g = context(), w;
+
+    g.font = vg.scene.fontString(o);
+    g.textAlign = a || "left";
+    g.textBaseline = b || "alphabetic";
+    w = g.measureText(o.text || "").width;
+
+    // horizontal
+    if (a === "center") {
+      x = x - (w / 2);
+    } else if (a === "right") {
+      x = x - w;
+    } else {
+      // left by default, do nothing
+    }
+
+    /// TODO find a robust solution for heights.
+    /// These offsets work for some but not all fonts.
+
+    // vertical
+    if (b === "top") {
+      y = y + (h/5);
+    } else if (b === "bottom") {
+      y = y - h;
+    } else if (b === "middle") {
+      y = y - (h/2) + (h/10);
+    } else {
+      y = y - 4*h/5; // alphabetic by default
+    }
+    
+    bounds.set(x, y, x+w, y+h);
+    if (o.angle && !noRotate) {
+      bounds.rotate(o.angle*Math.PI/180, o.x||0, o.y||0);
+    }
+    return bounds.expand(noRotate ? 0 : 1);
+  }
+
+  function group(g, bounds, includeLegends) {
+    var axes = g.axisItems || [],
+        legends = g.legendItems || [], j, m;
+
+    for (j=0, m=axes.length; j<m; ++j) {
+      bounds.union(axes[j].bounds);
+    }
+    for (j=0, m=g.items.length; j<m; ++j) {
+      bounds.union(g.items[j].bounds);
+    }
+    if (includeLegends) {
+      for (j=0, m=legends.length; j<m; ++j) {
+        bounds.union(legends[j].bounds);
+      }
+      if (g.width != null && g.height != null) {
+        bounds.add(g.width, g.height);
+      }
+      if (g.x != null && g.y != null) {
+        bounds.add(0, 0);
+      }
+    }
+    bounds.translate(g.x||0, g.y||0);
+    return bounds;
+  }
+
+  var methods = {
+    group:  group,
+    symbol: symbol,
+    image:  image,
+    rect:   rect,
+    rule:   rule,
+    arc:    arc,
+    text:   text,
+    path:   path,
+    area:   area,
+    line:   line
+  };
+
+  function itemBounds(item, func, opt) {
+    func = func || methods[item.mark.marktype];
+    if (!item.bounds_prev) item['bounds:prev'] = new vg.Bounds();
+    var b = item.bounds, pb = item['bounds:prev'];
+    if (b) pb.clear().union(b);
+    item.bounds = func(item, b ? b.clear() : new vg.Bounds(), opt);
+    if (!b) pb.clear().union(item.bounds);
+    return item.bounds;
+  }
+
+  function markBounds(mark, bounds, opt) {
+    bounds = bounds || mark.bounds && mark.bounds.clear() || new vg.Bounds();
+    var type  = mark.marktype,
+        func  = methods[type],
+        items = mark.items,
+        item, i, len;
+        
+    if (type==="area" || type==="line") {
+      items[0].bounds = func(items[0], bounds);
+    } else {
+      for (i=0, len=items.length; i<len; ++i) {
+        bounds.union(itemBounds(items[i], func, opt));
+      }
+    }
+    mark.bounds = bounds;
+  }
+  
+  return {
+    mark:  markBounds,
+    item:  itemBounds,
+    text:  text,
+    group: group
+  };
+
+})();vg.scene.encode = (function() {
+  var GROUP  = vg.scene.GROUP,
+      ENTER  = vg.scene.ENTER,
+      UPDATE = vg.scene.UPDATE,
+      EXIT   = vg.scene.EXIT,
+      EMPTY  = {};
+
+  function main(scene, def, trans, request, items) {
+    (request && items)
+      ? update.call(this, scene, def, trans, request, items)
+      : encode.call(this, scene, scene, def, trans, request);
+    return scene;
+  }
+  
+  function update(scene, def, trans, request, items) {
+    items = vg.array(items);
+    var i, len, item, group, props, prop;
+    for (i=0, len=items.length; i<len; ++i) {
+      item = items[i];
+      group = item.mark.group || null;
+      props = item.mark.def.properties;
+      prop = props && props[request];
+      if (prop) {
+        prop.call(vg, item, group, trans);
+        vg.scene.bounds.item(item);
+      }
+    }
+  }
+  
+  function encode(group, scene, def, trans, request) {
+    encodeItems.call(this, group, scene.items, def, trans, request);
+    if (scene.marktype === GROUP) {
+      encodeGroup.call(this, scene, def, group, trans, request);
+    } else {
+      vg.scene.bounds.mark(scene);
+    }
+  }
+  
+  function encodeLegend(group, scene, def, trans, request) {
+    encodeGroup.call(this, scene, def, group, trans, request);
+    encodeItems.call(this, group, scene.items, def, trans, request);
+    vg.scene.bounds.mark(scene, null, true);
+  }
+  
+  function encodeGroup(scene, def, parent, trans, request) {
+    var i, len, m, mlen, group, scales,
+        axes, axisItems, axisDef, leg, legItems, legDef;
+
+    for (i=0, len=scene.items.length; i<len; ++i) {
+      group = scene.items[i];
+
+      // cascade scales recursively
+      // use parent scales if there are no group-level scale defs
+      scales = group.scales || (group.scales =
+        def.scales ? vg.extend({}, parent.scales) : parent.scales);
+      
+      // update group-level scales
+      if (def.scales) {
+        vg.parse.scales(def.scales, scales, this._data, group);
+      }
+      
+      // update group-level axes
+      if (def.axes) {
+        axes = group.axes || (group.axes = []);
+        axisItems = group.axisItems || (group.axisItems = []);
+        vg.parse.axes(def.axes, axes, group.scales);
+        axes.forEach(function(a, i) {
+          axisDef = a.def();
+          axisItems[i] = vg.scene.build(axisDef, this._data, axisItems[i]);
+          axisItems[i].group = group;
+          encode.call(this, group, group.axisItems[i], axisDef, trans);
+        });
+      }
+      
+      // encode children marks
+      for (m=0, mlen=group.items.length; m<mlen; ++m) {
+        encode.call(this, group, group.items[m], def.marks[m], trans, request);
+      }
+    }
+    
+    // compute bounds (without legend)
+    vg.scene.bounds.mark(scene, null, !def.legends);
+    
+    // update legends
+    if (def.legends) {
+      for (i=0, len=scene.items.length; i<len; ++i) {
+        group = scene.items[i];
+        leg = group.legends || (group.legends = []);
+        legItems = group.legendItems || (group.legendItems = []);
+        vg.parse.legends(def.legends, leg, group.scales);
+        leg.forEach(function(l, i) {
+          legDef = l.def();
+          legItems[i] = vg.scene.build(legDef, this._data, legItems[i]);
+          legItems[i].group = group;
+          encodeLegend.call(this, group, group.legendItems[i], legDef, trans);
+        });
+      }
+      vg.scene.bounds.mark(scene, null, true);
+    }
+  }
+  
+  function encodeItems(group, items, def, trans, request) {    
+    var props  = def.properties || EMPTY,
+        enter  = props.enter,
+        update = props.update,
+        exit   = props.exit,
+        i, len, item, prop;
+
+    if (request) {
+      if (prop = props[request]) {
+        for (i=0, len=items.length; i<len; ++i) {
+          prop.call(vg, items[i], group, trans);
+        }
+      }
+      return; // exit early if given request
+    }
+
+    for (i=0; i<items.length; ++i) {
+      item = items[i];
+
+      // enter set
+      if (item.status === ENTER) {
+        if (enter) enter.call(vg, item, group);
+        item.status = UPDATE;
+      }
+
+      // update set      
+      if (item.status !== EXIT && update) {
+        update.call(vg, item, group, trans);
+      }
+      
+      // exit set
+      if (item.status === EXIT) {
+        if (exit) exit.call(vg, item, group, trans);
+        if (trans && !exit) trans.interpolate(item, EMPTY);
+        else if (!trans) items[i--].remove();
+      }
+    }
+  }
+  
+  return main;
+})();vg.scene.Transition = (function() {
+  function trans(duration, ease) {
+    this.duration = duration || 500;
+    this.ease = ease && d3.ease(ease) || d3.ease("cubic-in-out");
+    this.updates = {next: null};
+  }
+  
+  var prototype = trans.prototype;
+  
+  prototype.interpolate = function(item, values) {
+    var key, curr, next, interp, list = null;
+
+    for (key in values) {
+      curr = item[key];
+      next = values[key];      
+      if (curr !== next) {
+        if (key === "text") {
+          // skip interpolation for text labels
+          item[key] = next;
+        } else {
+          // otherwise lookup interpolator
+          interp = d3.interpolate(curr, next);
+          interp.property = key;
+          (list || (list=[])).push(interp);
+        }
+      }
+    }
+
+    if (list === null && item.status === vg.scene.EXIT) {
+      list = []; // ensure exiting items are included
+    }
+
+    if (list != null) {
+      list.item = item;
+      list.ease = item.mark.ease || this.ease;
+      list.next = this.updates.next;
+      this.updates.next = list;
+    }
+    return this;
+  };
+  
+  prototype.start = function(callback) {
+    var t = this, prev = t.updates, curr = prev.next;
+    for (; curr!=null; prev=curr, curr=prev.next) {
+      if (curr.item.status === vg.scene.EXIT) curr.remove = true;
+    }
+    t.callback = callback;
+    d3.timer(function(elapsed) { return step.call(t, elapsed); });
+  };
+
+  function step(elapsed) {
+    var list = this.updates, prev = list, curr = prev.next,
+        duration = this.duration,
+        item, delay, f, e, i, n, stop = true;
+
+    for (; curr!=null; prev=curr, curr=prev.next) {
+      item = curr.item;
+      delay = item.delay || 0;
+
+      f = (elapsed - delay) / duration;
+      if (f < 0) { stop = false; continue; }
+      if (f > 1) f = 1;
+      e = curr.ease(f);
+
+      for (i=0, n=curr.length; i<n; ++i) {
+        item[curr[i].property] = curr[i](e);
+        vg.scene.bounds.item(item);
+      }
+
+      if (f === 1) {
+        if (curr.remove) item.remove();
+        prev.next = curr.next;
+        curr = prev;
+      } else {
+        stop = false;
+      }
+    }
+
+    this.callback();
+    return stop;
+  };
+  
+  return trans;
+  
+})();
+
+vg.scene.transition = function(dur, ease) {
+  return new vg.scene.Transition(dur, ease);
+};vg.scene.axis = function() {
+  var scale,
+      orient = vg.config.axis.orient,
+      offset = 0,
+      titleOffset = vg.config.axis.titleOffset,
+      axisDef = null,
+      layer = "front",
+      grid = false,
+      title = null,
+      tickMajorSize = vg.config.axis.tickSize,
+      tickMinorSize = vg.config.axis.tickSize,
+      tickEndSize = vg.config.axis.tickSize,
+      tickPadding = vg.config.axis.padding,
+      tickValues = null,
+      tickFormat = null,
+      tickSubdivide = 0,
+      tickArguments = [vg.config.axis.ticks],
+      gridLineStyle = {},
+      tickLabelStyle = {},
+      majorTickStyle = {},
+      minorTickStyle = {},
+      titleStyle = {},
+      domainStyle = {};
+
+  var axis = {};
+
+  function reset() { axisDef = null; }
+
+  axis.def = function() {
+    var def = axisDef ? axisDef : (axisDef = axis_def(scale));
+    
+    // generate data
+    var major = tickValues == null
+      ? (scale.ticks ? scale.ticks.apply(scale, tickArguments) : scale.domain())
+      : tickValues;
+    var minor = vg_axisSubdivide(scale, major, tickSubdivide).map(vg.data.ingest);
+    major = major.map(vg.data.ingest);
+    var fmt = tickFormat==null ? (scale.tickFormat ? scale.tickFormat.apply(scale, tickArguments) : String) : tickFormat;
+    major.forEach(function(d) { d.label = fmt(d.data); });
+    var tdata = title ? [title].map(vg.data.ingest) : [];
+    
+    // update axis def
+    def.marks[0].from = function() { return grid ? major : []; };
+    def.marks[1].from = function() { return major; };
+    def.marks[2].from = function() { return minor; };
+    def.marks[3].from = def.marks[1].from;
+    def.marks[4].from = function() { return [1]; };
+    def.marks[5].from = function() { return tdata; };
+    def.offset = offset;
+    def.orient = orient;
+    def.layer = layer;
+    return def;
+  };
+
+  function axis_def(scale) {
+    // setup scale mapping
+    var newScale, oldScale, range;
+    if (scale.type === "ordinal") {
+      newScale = {scale: scale.scaleName, offset: 0.5 + scale.rangeBand()/2};
+      oldScale = newScale;
+    } else {
+      newScale = {scale: scale.scaleName, offset: 0.5};
+      oldScale = {scale: scale.scaleName+":prev", offset: 0.5};
+    }
+    range = vg_axisScaleRange(scale);
+
+    // setup axis marks
+    var gridLines = vg_axisTicks();
+    var majorTicks = vg_axisTicks();
+    var minorTicks = vg_axisTicks();
+    var tickLabels = vg_axisTickLabels();
+    var domain = vg_axisDomain();
+    var title = vg_axisTitle();
+    gridLines.properties.enter.stroke = {value: vg.config.axis.gridColor};
+
+    // extend axis marks based on axis orientation
+    vg_axisTicksExtend(orient, gridLines, oldScale, newScale, Infinity);
+    vg_axisTicksExtend(orient, majorTicks, oldScale, newScale, tickMajorSize);
+    vg_axisTicksExtend(orient, minorTicks, oldScale, newScale, tickMinorSize);
+    vg_axisLabelExtend(orient, tickLabels, oldScale, newScale, tickMajorSize, tickPadding);
+
+    vg_axisDomainExtend(orient, domain, range, tickEndSize);
+    vg_axisTitleExtend(orient, title, range, titleOffset); // TODO get offset
+    
+    // add / override custom style properties
+    vg.extend(gridLines.properties.update, gridLineStyle);
+    vg.extend(majorTicks.properties.update, majorTickStyle);
+    vg.extend(minorTicks.properties.update, minorTickStyle);
+    vg.extend(tickLabels.properties.update, tickLabelStyle);
+    vg.extend(domain.properties.update, domainStyle);
+    vg.extend(title.properties.update, titleStyle);
+
+    var marks = [gridLines, majorTicks, minorTicks, tickLabels, domain, title];
+    return {
+      type: "group",
+      interactive: false,
+      properties: { enter: vg_axisUpdate, update: vg_axisUpdate },
+      marks: marks.map(vg.parse.mark)
+    };
+  }
+
+  axis.scale = function(x) {
+    if (!arguments.length) return scale;
+    if (scale !== x) { scale = x; reset(); }
+    return axis;
+  };
+
+  axis.orient = function(x) {
+    if (!arguments.length) return orient;
+    if (orient !== x) {
+      orient = x in vg_axisOrients ? x + "" : vg.config.axis.orient;
+      reset();
+    }
+    return axis;
+  };
+
+  axis.title = function(x) {
+    if (!arguments.length) return title;
+    if (title !== x) { title = x; reset(); }
+    return axis;
+  };
+
+  axis.ticks = function() {
+    if (!arguments.length) return tickArguments;
+    tickArguments = arguments;
+    return axis;
+  };
+
+  axis.tickValues = function(x) {
+    if (!arguments.length) return tickValues;
+    tickValues = x;
+    return axis;
+  };
+
+  axis.tickFormat = function(x) {
+    if (!arguments.length) return tickFormat;
+    tickFormat = x;
+    return axis;
+  };
+  
+  axis.tickSize = function(x, y) {
+    if (!arguments.length) return tickMajorSize;
+    var n = arguments.length - 1,
+        major = +x,
+        minor = n > 1 ? +y : tickMajorSize,
+        end   = n > 0 ? +arguments[n] : tickMajorSize;
+
+    if (tickMajorSize !== major ||
+        tickMinorSize !== minor ||
+        tickEndSize !== end) {
+      reset();
+    }
+
+    tickMajorSize = major;
+    tickMinorSize = minor;
+    tickEndSize = end;
+    return axis;
+  };
+
+  axis.tickSubdivide = function(x) {
+    if (!arguments.length) return tickSubdivide;
+    tickSubdivide = +x;
+    return axis;
+  };
+  
+  axis.offset = function(x) {
+    if (!arguments.length) return offset;
+    offset = vg.isObject(x) ? x : +x;
+    return axis;
+  };
+
+  axis.tickPadding = function(x) {
+    if (!arguments.length) return tickPadding;
+    if (tickPadding !== +x) { tickPadding = +x; reset(); }
+    return axis;
+  };
+
+  axis.titleOffset = function(x) {
+    if (!arguments.length) return titleOffset;
+    if (titleOffset !== +x) { titleOffset = +x; reset(); }
+    return axis;
+  };
+
+  axis.layer = function(x) {
+    if (!arguments.length) return layer;
+    if (layer !== x) { layer = x; reset(); }
+    return axis;
+  };
+
+  axis.grid = function(x) {
+    if (!arguments.length) return grid;
+    if (grid !== x) { grid = x; reset(); }
+    return axis;
+  };
+
+  axis.gridLineProperties = function(x) {
+    if (!arguments.length) return gridLineStyle;
+    if (gridLineStyle !== x) { gridLineStyle = x; }
+    return axis;
+  };
+
+  axis.majorTickProperties = function(x) {
+    if (!arguments.length) return majorTickStyle;
+    if (majorTickStyle !== x) { majorTickStyle = x; }
+    return axis;
+  };
+
+  axis.minorTickProperties = function(x) {
+    if (!arguments.length) return minorTickStyle;
+    if (minorTickStyle !== x) { minorTickStyle = x; }
+    return axis;
+  };
+
+  axis.tickLabelProperties = function(x) {
+    if (!arguments.length) return tickLabelStyle;
+    if (tickLabelStyle !== x) { tickLabelStyle = x; }
+    return axis;
+  };
+
+  axis.titleProperties = function(x) {
+    if (!arguments.length) return titleStyle;
+    if (titleStyle !== x) { titleStyle = x; }
+    return axis;
+  };
+
+  axis.domainProperties = function(x) {
+    if (!arguments.length) return domainStyle;
+    if (domainStyle !== x) { domainStyle = x; }
+    return axis;
+  };
+  
+  axis.reset = function() { reset(); };
+
+  return axis;
+};
+
+var vg_axisOrients = {top: 1, right: 1, bottom: 1, left: 1};
+
+function vg_axisSubdivide(scale, ticks, m) {
+  subticks = [];
+  if (m && ticks.length > 1) {
+    var extent = vg_axisScaleExtent(scale.domain()),
+        subticks,
+        i = -1,
+        n = ticks.length,
+        d = (ticks[1] - ticks[0]) / ++m,
+        j,
+        v;
+    while (++i < n) {
+      for (j = m; --j > 0;) {
+        if ((v = +ticks[i] - j * d) >= extent[0]) {
+          subticks.push(v);
+        }
+      }
+    }
+    for (--i, j = 0; ++j < m && (v = +ticks[i] + j * d) < extent[1];) {
+      subticks.push(v);
+    }
+  }
+  return subticks;
+}
+
+function vg_axisScaleExtent(domain) {
+  var start = domain[0], stop = domain[domain.length - 1];
+  return start < stop ? [start, stop] : [stop, start];
+}
+
+function vg_axisScaleRange(scale) {
+  return scale.rangeExtent
+    ? scale.rangeExtent()
+    : vg_axisScaleExtent(scale.range());
+}
+
+var vg_axisAlign = {
+  bottom: "center",
+  top: "center",
+  left: "right",
+  right: "left"
+};
+
+var vg_axisBaseline = {
+  bottom: "top",
+  top: "bottom",
+  left: "middle",
+  right: "middle"
+};
+
+function vg_axisLabelExtend(orient, labels, oldScale, newScale, size, pad) {
+  size = Math.max(size, 0) + pad;
+  if (orient === "left" || orient === "top") {
+    size *= -1;
+  }  
+  if (orient === "top" || orient === "bottom") {
+    vg.extend(labels.properties.enter, {
+      x: oldScale,
+      y: {value: size},
+    });
+    vg.extend(labels.properties.update, {
+      x: newScale,
+      y: {value: size},
+      align: {value: "center"},
+      baseline: {value: vg_axisBaseline[orient]}
+    });
+  } else {
+    vg.extend(labels.properties.enter, {
+      x: {value: size},
+      y: oldScale,
+    });
+    vg.extend(labels.properties.update, {
+      x: {value: size},
+      y: newScale,
+      align: {value: vg_axisAlign[orient]},
+      baseline: {value: "middle"}
+    });
+  }
+}
+
+function vg_axisTicksExtend(orient, ticks, oldScale, newScale, size) {
+  var sign = (orient === "left" || orient === "top") ? -1 : 1;
+  if (size === Infinity) {
+    size = (orient === "top" || orient === "bottom")
+      ? {group: "mark.group.height", mult: -sign}
+      : {group: "mark.group.width", mult: -sign};
+  } else {
+    size = {value: sign * size};
+  }
+  if (orient === "top" || orient === "bottom") {
+    vg.extend(ticks.properties.enter, {
+      x:  oldScale,
+      y:  {value: 0},
+      y2: size
+    });
+    vg.extend(ticks.properties.update, {
+      x:  newScale,
+      y:  {value: 0},
+      y2: size
+    });
+    vg.extend(ticks.properties.exit, {
+      x:  newScale,
+    });        
+  } else {
+    vg.extend(ticks.properties.enter, {
+      x:  {value: 0},
+      x2: size,
+      y:  oldScale
+    });
+    vg.extend(ticks.properties.update, {
+      x:  {value: 0},
+      x2: size,
+      y:  newScale
+    });
+    vg.extend(ticks.properties.exit, {
+      y:  newScale,
+    });
+  }
+}
+
+function vg_axisTitleExtend(orient, title, range, offset) {
+  var mid = ~~((range[1] - range[0]) / 2),
+      sign = (orient === "top" || orient === "left") ? -1 : 1;
+  
+  if (orient === "bottom" || orient === "top") {
+    vg.extend(title.properties.update, {
+      x: {value: mid},
+      y: {value: sign*offset},
+      angle: {value: 0}
+    });
+  } else {
+    vg.extend(title.properties.update, {
+      x: {value: sign*offset},
+      y: {value: mid},
+      angle: {value: -90}
+    });
+  }
+}
+
+function vg_axisDomainExtend(orient, domain, range, size) {
+  var path;
+  if (orient === "top" || orient === "left") {
+    size = -1 * size;
+  }
+  if (orient === "bottom" || orient === "top") {
+    path = "M" + range[0] + "," + size + "V0H" + range[1] + "V" + size;
+  } else {
+    path = "M" + size + "," + range[0] + "H0V" + range[1] + "H" + size;
+  }
+  domain.properties.update.path = {value: path};
+}
+
+function vg_axisUpdate(item, group, trans) {
+  var o = trans ? {} : item,
+      offset = item.mark.def.offset,
+      orient = item.mark.def.orient,
+      width  = group.width,
+      height = group.height; // TODO fallback to global w,h?
+
+  if (vg.isObject(offset)) {
+    offset = -group.scales[offset.scale](offset.value);
+  }
+
+  switch (orient) {
+    case "left":   { o.x = -offset; o.y = 0; break; }
+    case "right":  { o.x = width + offset; o.y = 0; break; }
+    case "bottom": { o.x = 0; o.y = height + offset; break; }
+    case "top":    { o.x = 0; o.y = -offset; break; }
+    default:       { o.x = 0; o.y = 0; }
+  }
+
+  if (trans) trans.interpolate(item, o);
+}
+
+function vg_axisTicks() {
+  return {
+    type: "rule",
+    interactive: false,
+    key: "data",
+    properties: {
+      enter: {
+        stroke: {value: vg.config.axis.tickColor},
+        strokeWidth: {value: vg.config.axis.tickWidth},
+        opacity: {value: 1e-6}
+      },
+      exit: { opacity: {value: 1e-6} },
+      update: { opacity: {value: 1} }
+    }
+  };
+}
+
+function vg_axisTickLabels() {
+  return {
+    type: "text",
+    interactive: true,
+    key: "data",
+    properties: {
+      enter: {
+        fill: {value: vg.config.axis.tickLabelColor},
+        font: {value: vg.config.axis.tickLabelFont},
+        fontSize: {value: vg.config.axis.tickLabelFontSize},
+        opacity: {value: 1e-6},
+        text: {field: "label"}
+      },
+      exit: { opacity: {value: 1e-6} },
+      update: { opacity: {value: 1} }
+    }
+  };
+}
+
+function vg_axisTitle() {
+  return {
+    type: "text",
+    interactive: true,
+    properties: {
+      enter: {
+        font: {value: vg.config.axis.titleFont},
+        fontSize: {value: vg.config.axis.titleFontSize},
+        fontWeight: {value: vg.config.axis.titleFontWeight},
+        fill: {value: vg.config.axis.titleColor},
+        align: {value: "center"},
+        baseline: {value: "middle"},
+        text: {field: "data"}
+      },
+      update: {}
+    }
+  };
+}
+
+function vg_axisDomain() {
+  return {
+    type: "path",
+    interactive: false,
+    properties: {
+      enter: {
+        x: {value: 0.5},
+        y: {value: 0.5},
+        stroke: {value: vg.config.axis.axisColor},
+        strokeWidth: {value: vg.config.axis.axisWidth}
+      },
+      update: {}
+    }
+  };
+}
+vg.scene.legend = function() {
+  var size = null,
+      shape = null,
+      fill = null,
+      stroke = null,
+      spacing = null,
+      values = null,
+      format = null,
+      title = undefined,
+      orient = "right",
+      offset = vg.config.legend.offset,
+      padding = vg.config.legend.padding,
+      legendDef,
+      tickArguments = [5],
+      legendStyle = {},
+      symbolStyle = {},
+      gradientStyle = {},
+      titleStyle = {},
+      labelStyle = {};
+
+  var legend = {},
+      legendDef = null;
+
+  function reset() { legendDef = null; }
+
+  legend.def = function() {
+    var scale = size || shape || fill || stroke; 
+    if (!legendDef) {
+      legendDef = (scale===fill || scale===stroke) && !discrete(scale.type)
+        ? quantDef(scale)
+        : ordinalDef(scale);      
+    }
+    legendDef.orient = orient;
+    legendDef.offset = offset;
+    legendDef.padding = padding;
+    return legendDef;
+  };
+
+  function discrete(type) {
+    return type==="ordinal" || type==="quantize"
+      || type==="quantile" || type==="threshold";
+  }
+
+  function ordinalDef(scale) {
+    var def = o_legend_def(size, shape, fill, stroke);
+
+    // generate data
+    var data = (values == null
+      ? (scale.ticks ? scale.ticks.apply(scale, tickArguments) : scale.domain())
+      : values).map(vg.data.ingest);
+    var fmt = format==null ? (scale.tickFormat ? scale.tickFormat.apply(scale, tickArguments) : String) : format;
+    
+    // determine spacing between legend entries
+    var fs, range, offset, pad=5, domain = d3.range(data.length);
+    if (size) {
+      range = data.map(function(x) { return Math.sqrt(size(x.data)); });
+      offset = d3.max(range);
+      range = range.reduce(function(a,b,i,z) {
+          if (i > 0) a[i] = a[i-1] + z[i-1]/2 + pad;
+          return (a[i] += b/2, a); }, [0]).map(Math.round);
+    } else {
+      offset = Math.round(Math.sqrt(vg.config.legend.symbolSize));
+      range = spacing
+        || (fs = labelStyle.fontSize) && (fs.value + pad)
+        || (vg.config.legend.labelFontSize + pad);
+      range = domain.map(function(d,i) {
+        return Math.round(offset/2 + i*range);
+      });
+    }
+
+    // account for padding and title size
+    var sz = padding, ts;
+    if (title) {
+      ts = titleStyle.fontSize;
+      sz += 5 + ((ts && ts.value) || vg.config.legend.titleFontSize);
+    }
+    for (var i=0, n=range.length; i<n; ++i) range[i] += sz;
+    
+    // build scale for label layout
+    var scale = {
+      name: "legend",
+      type: "ordinal",
+      points: true,
+      domain: domain,
+      range: range
+    };
+    
+    // update legend def
+    var tdata = (title ? [title] : []).map(vg.data.ingest);
+    data.forEach(function(d) {
+      d.label = fmt(d.data);
+      d.offset = offset;
+    });
+    def.scales = [ scale ];
+    def.marks[0].from = function() { return tdata; };
+    def.marks[1].from = function() { return data; };
+    def.marks[2].from = def.marks[1].from;
+    return def;
+  }
+
+  function o_legend_def(size, shape, fill, stroke) {
+    // setup legend marks
+    var titles = vg_legendTitle(),
+        symbols = vg_legendSymbols(),
+        labels = vg_vLegendLabels();
+
+    // extend legend marks
+    vg_legendSymbolExtend(symbols, size, shape, fill, stroke);
+    
+    // add / override custom style properties
+    vg.extend(titles.properties.update, titleStyle);
+    vg.extend(symbols.properties.update, symbolStyle);
+    vg.extend(labels.properties.update, labelStyle);
+
+    // padding from legend border
+    titles.properties.enter.x.value += padding;
+    titles.properties.enter.y.value += padding;
+    labels.properties.enter.x.offset += padding + 1;
+    symbols.properties.enter.x.offset = padding + 1;
+
+    return {
+      type: "group",
+      interactive: false,
+      properties: {
+        enter: vg.parse.properties("group", legendStyle),
+        update: vg_legendUpdate
+      },
+      marks: [titles, symbols, labels].map(vg.parse.mark)
+    };
+  }
+
+  function quantDef(scale) {
+    var def = q_legend_def(scale),
+        dom = scale.domain(),
+        data = dom.map(vg.data.ingest),
+        width = (gradientStyle.width && gradientStyle.width.value) || vg.config.legend.gradientWidth,
+        fmt = format==null ? (scale.tickFormat ? scale.tickFormat.apply(scale, tickArguments) : String) : format;
+
+    // build scale for label layout
+    var layout = {
+      name: "legend",
+      type: scale.type,
+      round: true,
+      zero: false,
+      domain: [dom[0], dom[dom.length-1]],
+      range: [padding, width+padding]
+    };
+    if (scale.type==="pow") layout.exponent = scale.exponent();
+    
+    // update legend def
+    var tdata = (title ? [title] : []).map(vg.data.ingest);
+    data.forEach(function(d,i) {
+      d.label = fmt(d.data);
+      d.align = i==(data.length-1) ? "right" : i==0 ? "left" : "center";
+    });
+    def.scales = [ layout ];
+    def.marks[0].from = function() { return tdata; };
+    def.marks[1].from = function() { return [1]; };
+    def.marks[2].from = function() { return data; };
+    return def;
+  }
+  
+  function q_legend_def(scale) {
+    // setup legend marks
+    var titles = vg_legendTitle(),
+        gradient = vg_legendGradient(),
+        labels = vg_hLegendLabels(),
+        grad = new vg.Gradient();
+
+    // setup color gradient
+    var dom = scale.domain(),
+        min = dom[0],
+        max = dom[dom.length-1],
+        f = scale.copy().domain([min, max]).range([0,1]);
+        
+    var stops = (scale.type !== "linear" && scale.ticks)
+      ? scale.ticks.call(scale, 15) : dom;
+    if (min !== stops[0]) stops.unshift(min);
+    if (max !== stops[stops.length-1]) stops.push(max);
+
+    for (var i=0, n=stops.length; i<n; ++i) {
+      grad.stop(f(stops[i]), scale(stops[i]));
+    }
+    gradient.properties.enter.fill = {value: grad};
+
+    // add / override custom style properties
+    vg.extend(titles.properties.update, titleStyle);
+    vg.extend(gradient.properties.update, gradientStyle);
+    vg.extend(labels.properties.update, labelStyle);
+
+    // account for gradient size
+    var gp = gradient.properties, gh = gradientStyle.height,
+        hh = (gh && gh.value) || gp.enter.height.value;
+    labels.properties.enter.y.value = hh;
+
+    // account for title size as needed
+    if (title) {
+      var tp = titles.properties, fs = titleStyle.fontSize,
+          sz = 4 + ((fs && fs.value) || tp.enter.fontSize.value);
+      gradient.properties.enter.y.value += sz;
+      labels.properties.enter.y.value += sz;
+    }
+    
+    // padding from legend border
+    titles.properties.enter.x.value += padding;
+    titles.properties.enter.y.value += padding;
+    gradient.properties.enter.x.value += padding;
+    gradient.properties.enter.y.value += padding;
+    labels.properties.enter.y.value += padding;
+
+    return {
+      type: "group",
+      interactive: false,
+      properties: {
+        enter: vg.parse.properties("group", legendStyle),
+        update: vg_legendUpdate
+      },
+      marks: [titles, gradient, labels].map(vg.parse.mark)
+    };
+  }
+
+  legend.size = function(x) {
+    if (!arguments.length) return size;
+    if (size !== x) { size = x; reset(); }
+    return legend;
+  };
+
+  legend.shape = function(x) {
+    if (!arguments.length) return shape;
+    if (shape !== x) { shape = x; reset(); }
+    return legend;
+  };
+
+  legend.fill = function(x) {
+    if (!arguments.length) return fill;
+    if (fill !== x) { fill = x; reset(); }
+    return legend;
+  };
+  
+  legend.stroke = function(x) {
+    if (!arguments.length) return stroke;
+    if (stroke !== x) { stroke = x; reset(); }
+    return legend;
+  };
+
+  legend.title = function(x) {
+    if (!arguments.length) return title;
+    if (title !== x) { title = x; reset(); }
+    return legend;
+  };
+
+  legend.format = function(x) {
+    if (!arguments.length) return format;
+    if (format !== x) { format = x; reset(); }
+    return legend;
+  };
+
+  legend.spacing = function(x) {
+    if (!arguments.length) return spacing;
+    if (spacing !== +x) { spacing = +x; reset(); }
+    return legend;
+  };
+
+  legend.orient = function(x) {
+    if (!arguments.length) return orient;
+    orient = x in vg_legendOrients ? x + "" : vg.config.legend.orient;
+    return legend;
+  };
+
+  legend.offset = function(x) {
+    if (!arguments.length) return offset;
+    offset = +x;
+    return legend;
+  };
+
+  legend.values = function(x) {
+    if (!arguments.length) return values;
+    values = x;
+    return legend;
+  };
+
+  legend.legendProperties = function(x) {
+    if (!arguments.length) return legendStyle;
+    legendStyle = x;
+    return legend;
+  };
+
+  legend.symbolProperties = function(x) {
+    if (!arguments.length) return symbolStyle;
+    symbolStyle = x;
+    return legend;
+  };
+
+  legend.gradientProperties = function(x) {
+    if (!arguments.length) return gradientStyle;
+    gradientStyle = x;
+    return legend;
+  };
+
+  legend.labelProperties = function(x) {
+    if (!arguments.length) return labelStyle;
+    labelStyle = x;
+    return legend;
+  };
+  
+  legend.titleProperties = function(x) {
+    if (!arguments.length) return titleStyle;
+    titleStyle = x;
+    return legend;
+  };
+
+  legend.reset = function() { reset(); };
+
+  return legend;
+};
+
+var vg_legendOrients = {right: 1, left: 1};
+
+function vg_legendUpdate(item, group, trans) {
+  var o = trans ? {} : item,
+      offset = item.mark.def.offset,
+      orient = item.mark.def.orient,
+      pad    = item.mark.def.padding * 2,
+      gx1    = group.bounds ? group.bounds.x1 : 0,
+      gx2    = group.bounds ? group.bounds.x2 : group.width,
+      lw     = ~~item.bounds.width() + (o.width ? 0 : pad),
+      lh     = ~~item.bounds.height() + (o.height ? 0 : pad);
+
+  o.x = 0.5;
+  o.y = 0.5;
+  o.width = lw;
+  o.height = lh;
+
+  switch (orient) {
+    case "left":  { o.x += gx1 - offset - lw; break; };
+    case "right": { o.x += gx2 + offset; break; };
+  }
+  
+  item.mark.def.properties.enter(item, group, trans);
+}
+
+function vg_legendSymbolExtend(mark, size, shape, fill, stroke) {
+  var props = mark.properties.enter;
+  if (size)   props.size   = {scale: size.scaleName,   field: "data"};
+  if (shape)  props.shape  = {scale: shape.scaleName,  field: "data"};
+  if (fill)   props.fill   = {scale: fill.scaleName,   field: "data"};
+  if (stroke) props.stroke = {scale: stroke.scaleName, field: "data"};
+}
+
+function vg_legendTitle() {
+  var cfg = vg.config.legend;
+  return {
+    type: "text",
+    interactive: false,
+    key: "data",
+    properties: {
+      enter: {
+        x: {value: 0},
+        y: {value: 0},
+        fill: {value: cfg.titleColor},
+        font: {value: cfg.titleFont},
+        fontSize: {value: cfg.titleFontSize},
+        fontWeight: {value: cfg.titleFontWeight},
+        baseline: {value: "top"},
+        text: {field: "data"},
+        opacity: {value: 1e-6}
+      },
+      exit: { opacity: {value: 1e-6} },
+      update: { opacity: {value: 1} }
+    }
+  };
+}
+
+function vg_legendSymbols() {
+  var cfg = vg.config.legend;
+  return {
+    type: "symbol",
+    interactive: false,
+    key: "data",
+    properties: {
+      enter: {
+        x: {field: "offset", mult: 0.5},
+        y: {scale: "legend", field: "index"},
+        shape: {value: cfg.symbolShape},
+        size: {value: cfg.symbolSize},
+        stroke: {value: cfg.symbolColor},
+        strokeWidth: {value: cfg.symbolStrokeWidth},
+        opacity: {value: 1e-6}
+      },
+      exit: { opacity: {value: 1e-6} },
+      update: { opacity: {value: 1} }
+    }
+  };
+}
+
+function vg_vLegendLabels() {
+  var cfg = vg.config.legend;
+  return {
+    type: "text",
+    interactive: false,
+    key: "data",
+    properties: {
+      enter: {
+        x: {field: "offset", offset: 5},
+        y: {scale: "legend", field: "index"},
+        fill: {value: cfg.labelColor},
+        font: {value: cfg.labelFont},
+        fontSize: {value: cfg.labelFontSize},
+        align: {value: cfg.labelAlign},
+        baseline: {value: cfg.labelBaseline},
+        text: {field: "label"},
+        opacity: {value: 1e-6}
+      },
+      exit: { opacity: {value: 1e-6} },
+      update: { opacity: {value: 1} }
+    }
+  };
+}
+
+function vg_legendGradient() {
+  var cfg = vg.config.legend;
+  return {
+    type: "rect",
+    interactive: false,
+    properties: {
+      enter: {
+        x: {value: 0},
+        y: {value: 0},
+        width: {value: cfg.gradientWidth},
+        height: {value: cfg.gradientHeight},
+        stroke: {value: cfg.gradientStrokeColor},
+        strokeWidth: {value: cfg.gradientStrokeWidth},
+        opacity: {value: 1e-6}
+      },
+      exit: { opacity: {value: 1e-6} },
+      update: { opacity: {value: 1} }
+    }
+  };
+}
+
+function vg_hLegendLabels() {
+  var cfg = vg.config.legend;
+  return {
+    type: "text",
+    interactive: false,
+    key: "data",
+    properties: {
+      enter: {
+        x: {scale: "legend", field: "data"},
+        y: {value: 20},
+        dy: {value: 2},
+        fill: {value: cfg.labelColor},
+        font: {value: cfg.labelFont},
+        fontSize: {value: cfg.labelFontSize},
+        align: {field: "align"},
+        baseline: {value: "top"},
+        text: {field: "label"},
+        opacity: {value: 1e-6}
+      },
+      exit: { opacity: {value: 1e-6} },
+      update: { opacity: {value: 1} }
+    }
+  };
+}vg.Model = (function() {
+  function model() {
+    this._defs = null;
+    this._data = {};
+    this._scene = null;
+    this._reset = false;
+  }
+  
+  var prototype = model.prototype;
+  
+  prototype.defs = function(defs) {
+    if (!arguments.length) return this._defs;
+    this._defs = defs;
+    return this;
+  };
+  
+  prototype.data = function(data) {
+    if (!arguments.length) return this._data;
+
+    var tx = this._defs.data.flow || {},
+        keys = this._defs.data.defs.map(vg.accessor("name")),
+        len = keys.length, i, k;
+
+    for (i=0; i<len; ++i) {
+      if (!data[k=keys[i]]) continue;
+      this.ingest(k, tx, data[k]);
+    }
+
+    return this;
+  };
+  
+  prototype.ingest = function(name, tx, input) {
+    this._data[name] = tx[name]
+      ? tx[name](input, this._data, this._defs.marks)
+      : input;
+    this.dependencies(name, tx);
+  };
+  
+  prototype.dependencies = function(name, tx) {
+    var source = this._defs.data.source[name],
+        data = this._data[name],
+        n = source ? source.length : 0, i, x;
+    for (i=0; i<n; ++i) {
+      x = vg_data_duplicate(data);
+      if (vg.isTree(data)) vg_make_tree(x);
+      this.ingest(source[i], tx, x);
+    }
+  };
+  
+  prototype.width = function(width) {
+    if (this._defs) this._defs.width = width;
+    if (this._defs && this._defs.marks) this._defs.marks.width = width;
+    if (this._scene) this._scene.items[0].width = width;
+    this._reset = true;
+    return this;
+  };
+  
+  prototype.height = function(height) {
+    if (this._defs) this._defs.height = height;
+    if (this._defs && this._defs.marks) this._defs.marks.height = height;
+    if (this._scene) this._scene.items[0].height = height;
+    this._reset = true;
+    return this;
+  };
+  
+  prototype.scene = function(node) {
+    if (!arguments.length) return this._scene;
+    this._scene = node;
+    return this;
+  };
+  
+  prototype.build = function() {
+    var m = this, data = m._data, marks = m._defs.marks;
+    m._scene = vg.scene.build.call(m, marks, data, m._scene);
+    m._scene.items[0].width = marks.width;
+    m._scene.items[0].height = marks.height;
+    m._scene.interactive = false;
+    return this;
+  };
+  
+  prototype.encode = function(trans, request, item) {
+    if (this._reset) { this.reset(); this._reset = false; }
+    var m = this, scene = m._scene, defs = m._defs;
+    vg.scene.encode.call(m, scene, defs.marks, trans, request, item);
+    return this;
+  };
+
+  prototype.reset = function() {
+    if (this._scene) {
+      vg.scene.visit(this._scene, function(item) {
+        if (item.axes) item.axes.forEach(function(axis) { axis.reset(); });
+      });
+    }
+    return this;
+  };
+
+  return model;
+})();vg.View = (function() {
+  var view = function(el, width, height) {
+    this._el = null;
+    this._build = false;
+    this._model = new vg.Model();
+    this._width = this.__width = width || 500;
+    this._height = this.__height = height || 500;
+    this._autopad = 1;
+    this._padding = {top:0, left:0, bottom:0, right:0};
+    this._viewport = null;
+    this._renderer = null;
+    this._handler = null;
+    this._io = vg.canvas;
+    if (el) this.initialize(el);
+  };
+  
+  var prototype = view.prototype;
+  
+  prototype.width = function(width) {
+    if (!arguments.length) return this.__width;
+    if (this.__width !== width) {
+      this._width = this.__width = width;
+      if (this._el) this.initialize(this._el.parentNode);
+      this._model.width(width);
+      if (this._strict) this._autopad = 1;
+    }
+    return this;
+  };
+
+  prototype.height = function(height) {
+    if (!arguments.length) return this.__height;
+    if (this.__height !== height) {
+      this._height = this.__height = height;
+      if (this._el) this.initialize(this._el.parentNode);
+      this._model.height(this._height);
+      if (this._strict) this._autopad = 1;
+    }
+    return this;
+  };
+
+  prototype.padding = function(pad) {
+    if (!arguments.length) return this._padding;
+    if (this._padding !== pad) {
+      if (vg.isString(pad)) {
+        this._autopad = 1;
+        this._padding = {top:0, left:0, bottom:0, right:0};
+        this._strict = (pad === "strict");
+      } else {
+        this._autopad = 0;
+        this._padding = pad;
+        this._strict = false;
+      }
+      if (this._el) {
+        this._renderer.resize(this._width, this._height, pad);
+        this._handler.padding(pad);
+      }
+    }
+    return this;
+  };
+  
+  prototype.autopad = function(opt) {
+    if (this._autopad < 1) return this;
+    else this._autopad = 0;
+
+    var pad = this._padding,
+        b = this.model().scene().bounds,
+        inset = vg.config.autopadInset,
+        l = b.x1 < 0 ? Math.ceil(-b.x1) + inset : 0,
+        t = b.y1 < 0 ? Math.ceil(-b.y1) + inset : 0,
+        r = b.x2 > this._width  ? Math.ceil(+b.x2 - this._width) + inset : 0,
+        b = b.y2 > this._height ? Math.ceil(+b.y2 - this._height) + inset : 0;
+    pad = {left:l, top:t, right:r, bottom:b};
+
+    if (this._strict) {
+      this._autopad = 0;
+      this._padding = pad;
+      this._width = Math.max(0, this.__width - (l+r));
+      this._height = Math.max(0, this.__height - (t+b));
+      this._model.width(this._width);
+      this._model.height(this._height);
+      if (this._el) this.initialize(this._el.parentNode);
+      this.update({props:"enter"}).update({props:"update"});
+    } else {
+      this.padding(pad).update(opt);
+    }
+    return this;
+  };
+
+  prototype.viewport = function(size) {
+    if (!arguments.length) return this._viewport;
+    if (this._viewport !== size) {
+      this._viewport = size;
+      if (this._el) this.initialize(this._el.parentNode);
+    }
+    return this;
+  };
+  
+  prototype.renderer = function(type) {
+    if (!arguments.length) return this._io;
+    if (type === "canvas") type = vg.canvas;
+    if (type === "svg") type = vg.svg;
+    if (this._io !== type) {
+      this._io = type;
+      this._renderer = null;
+      if (this._el) this.initialize(this._el.parentNode);
+      if (this._build) this.render();
+    }
+    return this;
+  };
+
+  prototype.defs = function(defs) {
+    if (!arguments.length) return this._model.defs();
+    this._model.defs(defs);
+    return this;
+  };
+
+  prototype.data = function(data) {
+    if (!arguments.length) return this._model.data();
+    var ingest = vg.keys(data).reduce(function(d, k) {
+      return (d[k] = vg.data.ingestAll(data[k]), d);
+    }, {});
+    this._model.data(ingest);
+    this._build = false;
+    return this;
+  };
+
+  prototype.model = function(model) {
+    if (!arguments.length) return this._model;
+    if (this._model !== model) {
+      this._model = model;
+      if (this._handler) this._handler.model(model);
+    }
+    return this;
+  };
+
+  prototype.initialize = function(el) {
+    var v = this, prevHandler,
+        w = v._width, h = v._height, pad = v._padding;
+    
+    // clear pre-existing container
+    d3.select(el).select("div.vega").remove();
+    
+    // add div container
+    this._el = el = d3.select(el)
+      .append("div")
+      .attr("class", "vega")
+      .style("position", "relative")
+      .node();
+    if (v._viewport) {
+      d3.select(el)
+        .style("width",  (v._viewport[0] || w)+"px")
+        .style("height", (v._viewport[1] || h)+"px")
+        .style("overflow", "auto");
+    }
+    
+    // renderer
+    v._renderer = (v._renderer || new this._io.Renderer())
+      .initialize(el, w, h, pad);
+    
+    // input handler
+    prevHandler = v._handler;
+    v._handler = new this._io.Handler()
+      .initialize(el, pad, v)
+      .model(v._model);
+
+    if (prevHandler) {
+      prevHandler.handlers().forEach(function(h) {
+        v._handler.on(h.type, h.handler);
+      });
+    }
+    
+    return this;
+  };
+  
+  prototype.render = function(items) {
+    this._renderer.render(this._model.scene(), items);
+    return this;
+  };
+  
+  prototype.on = function() {
+    this._handler.on.apply(this._handler, arguments);
+    return this;
+  };
+  
+  prototype.off = function() {
+    this._handler.off.apply(this._handler, arguments);
+    return this;
+  };
+  
+  prototype.update = function(opt) {    
+    opt = opt || {};
+    var view = this,
+        trans = opt.duration
+          ? vg.scene.transition(opt.duration, opt.ease)
+          : null;
+
+    view._build = view._build || (view._model.build(), true);
+    view._model.encode(trans, opt.props, opt.items);
+    
+    if (trans) {
+      trans.start(function(items) {
+        view._renderer.render(view._model.scene(), items);
+      });
+    }
+    else view.render(opt.items);
+
+    return view.autopad(opt);
+  };
+      
+  return view;
+})();
+
+// view constructor factory
+// takes definitions from parsed specification as input
+// returns a view constructor
+vg.ViewFactory = function(defs) {
+  return function(opt) {
+    opt = opt || {};
+    var v = new vg.View()
+      .width(defs.width)
+      .height(defs.height)
+      .padding(defs.padding)
+      .viewport(defs.viewport)
+      .renderer(opt.renderer || "canvas")
+      .defs(defs);
+
+    if (defs.data.load) v.data(defs.data.load);
+    if (opt.data) v.data(opt.data);
+    if (opt.el) v.initialize(opt.el);
+
+    if (opt.hover !== false) {
+      v.on("mouseover", function(evt, item) {
+        if (item.hasPropertySet("hover")) {
+          this.update({props:"hover", items:item});
+        }
+      })
+      .on("mouseout", function(evt, item) {
+        if (item.hasPropertySet("hover")) {
+          this.update({props:"update", items:item});
+        }
+      });
+    }
+  
+    return v;
+  };
+};
+vg.Spec = (function() {
+  var spec = function(s) {
+    this.spec = {
+      width: 500,
+      height: 500,
+      padding: 0,
+      data: [],
+      scales: [],
+      axes: [],
+      marks: []
+    };
+    if (s) vg.extend(this.spec, s);
+  };
+  
+  var prototype = spec.prototype;
+
+  prototype.width = function(w) {
+    this.spec.width = w;
+    return this;
+  };
+  
+  prototype.height = function(h) {
+    this.spec.height = h;
+    return this;
+  };
+  
+  prototype.padding = function(p) {
+    this.spec.padding = p;
+    return this;
+  };
+  
+  prototype.viewport = function(v) {
+    this.spec.viewport = v;
+    return this;
+  };
+
+  prototype.data = function(name, params) {
+    if (!params) params = vg.isString(name) ? {name: name} : name;
+    else params.name = name;
+    this.spec.data.push(params);
+    return this;
+  };
+  
+  prototype.scale = function(name, params) {
+    if (!params) params = vg.isString(name) ? {name: name} : name;
+    else params.name = name;
+    this.spec.scales.push(params);
+    return this;
+  };
+  
+  prototype.axis = function(params) {
+    this.spec.axes.push(params);
+    return this;
+  };
+  
+  prototype.mark = function(type, mark) {
+    if (!mark) mark = {type: type};
+    else mark.type = type;
+    mark.properties = {};
+    this.spec.marks.push(mark);
+    
+    var that = this;
+    return {
+      from: function(name, obj) {
+              mark.from = obj
+                ? (obj.data = name, obj)
+                : vg.isString(name) ? {data: name} : name;
+              return this;
+            },
+      prop: function(name, obj) {
+              mark.properties[name] = vg.keys(obj).reduce(function(o,k) {
+                var v = obj[k];
+                return (o[k] = vg.isObject(v) ? v : {value: v}, o);
+              }, {});
+              return this;
+            },
+      done: function() { return that; }
+    };
+  };
+
+  prototype.parse = function(callback) {
+    vg.parse.spec(this.spec, callback);
+  };
+
+  prototype.json = function() {
+    return this.spec;
+  };
+
+  return spec;
+})();
+
+vg.spec = function(s) {
+  return new vg.Spec(s);
+};
+vg.headless = {};vg.headless.View = (function() {
+  
+  var view = function(width, height, pad, type) {
+    this._canvas = null;
+    this._type = type;
+    this._el = "body";
+    this._build = false;
+    this._model = new vg.Model();
+    this._width = this.__width = width || 500;
+    this._height = this.__height = height || 500;
+    this._autopad = 1;
+    this._padding = pad || {top:0, left:0, bottom:0, right:0};
+    this._renderer = new vg[type].Renderer();
+    this.initialize();
+  };
+  
+  var prototype = view.prototype;
+
+  prototype.el = function(el) {
+    if (!arguments.length) return this._el;
+    if (this._el !== el) {
+      this._el = el;
+      this.initialize();
+    }
+    return this;
+  };
+
+  prototype.width = function(width) {
+    if (!arguments.length) return this._width;
+    if (this._width !== width) {
+      this._width = width;
+      this.initialize();
+      this._model.width(width);
+    }
+    return this;
+  };
+
+  prototype.height = function(height) {
+    if (!arguments.length) return this._height;
+    if (this._height !== height) {
+      this._height = height;
+      this.initialize();
+      this._model.height(this._height);
+    }
+    return this;
+  };
+
+  prototype.padding = function(pad) {
+    if (!arguments.length) return this._padding;
+    if (this._padding !== pad) {
+      if (vg.isString(pad)) {
+        this._autopad = 1;
+        this._padding = {top:0, left:0, bottom:0, right:0};
+        this._strict = (pad === "strict");
+      } else {
+        this._autopad = 0;
+        this._padding = pad;
+        this._strict = false;
+      }
+      this.initialize();
+    }
+    return this;
+  };
+
+  prototype.autopad = function(opt) {
+    if (this._autopad < 1) return this;
+    else this._autopad = 0;
+
+    var pad = this._padding,
+        b = this._model.scene().bounds,
+        inset = vg.config.autopadInset,
+        l = b.x1 < 0 ? Math.ceil(-b.x1) + inset : 0,
+        t = b.y1 < 0 ? Math.ceil(-b.y1) + inset : 0,
+        r = b.x2 > this._width  ? Math.ceil(+b.x2 - this._width) + inset : 0,
+        b = b.y2 > this._height ? Math.ceil(+b.y2 - this._height) + inset : 0;
+    pad = {left:l, top:t, right:r, bottom:b};
+
+    if (this._strict) {
+      this._autopad = 0;
+      this._padding = pad;
+      this._width = Math.max(0, this.__width - (l+r));
+      this._height = Math.max(0, this.__height - (t+b));
+      this._model.width(this._width);
+      this._model.height(this._height);
+      if (this._el) this.initialize();
+      this.update({props:"enter"}).update({props:"update"});
+    } else {
+      this.padding(pad).update(opt);
+    }
+    return this;
+  };
+
+  prototype.viewport = function() {
+    if (!arguments.length) return null;
+    return this;
+  };
+
+  prototype.defs = function(defs) {
+    if (!arguments.length) return this._model.defs();
+    this._model.defs(defs);
+    return this;
+  };
+
+  prototype.data = function(data) {
+    if (!arguments.length) return this._model.data();
+    var ingest = vg.keys(data).reduce(function(d, k) {
+      return (d[k] = vg.data.ingestAll(data[k]), d);
+    }, {});
+    this._model.data(ingest);
+    this._build = false;
+    return this;
+  };
+
+  prototype.renderer = function() {
+    return this._renderer;
+  };
+
+  prototype.canvas = function() {
+    return this._canvas;
+  };
+  
+  prototype.canvasAsync = function(callback) {
+    var r = this._renderer, view = this;
+    
+    function wait() {
+      if (r.pendingImages() === 0) {
+        view.render(); // re-render with all images
+        callback(view._canvas);
+      } else {
+        setTimeout(wait, 10);
+      }
+    }
+
+    // if images loading, poll until ready
+    (r.pendingImages() > 0) ? wait() : callback(this._canvas);
+  };
+  
+  prototype.svg = function() {
+    if (this._type !== "svg") return null;
+
+    var p = this._padding,
+        w = this._width  + (p ? p.left + p.right : 0),
+        h = this._height + (p ? p.top + p.bottom : 0);
+
+      // build svg text
+    var svg = d3.select(this._el)
+      .select("svg").node().innerHTML
+      .replace(/ href=/g, " xlink:href="); // ns hack. sigh.
+
+    return '<svg '
+      + 'width="' + w + '" '
+      + 'height="' + h + '" '
+      + vg.config.svgNamespace + '>' + svg + '</svg>'
+  };
+
+  prototype.initialize = function() {    
+    var w = this._width,
+        h = this._height,
+        pad = this._padding;
+    
+    if (this._type === "svg") {
+      this.initSVG(w, h, pad);
+    } else {
+      this.initCanvas(w, h, pad);
+    }
+    
+    return this;
+  };
+  
+  prototype.initCanvas = function(w, h, pad) {
+    var Canvas = require("canvas"),
+        tw = w + pad.left + pad.right,
+        th = h + pad.top + pad.bottom,
+        canvas = this._canvas = new Canvas(tw, th),
+        ctx = canvas.getContext("2d");
+    
+    // setup canvas context
+    ctx.setTransform(1, 0, 0, 1, pad.left, pad.top);
+
+    // configure renderer
+    this._renderer.context(ctx);
+    this._renderer.resize(w, h, pad);
+  };
+  
+  prototype.initSVG = function(w, h, pad) {
+    var tw = w + pad.left + pad.right,
+        th = h + pad.top + pad.bottom;
+
+    // configure renderer
+    this._renderer.initialize(this._el, w, h, pad);
+  }
+  
+  prototype.render = function(items) {
+    this._renderer.render(this._model.scene(), items);
+    return this;
+  };
+  
+  prototype.update = function(opt) {
+    opt = opt || {};
+    var view = this;
+    view._build = view._build || (view._model.build(), true);
+    view._model.encode(null, opt.props, opt.items);
+    view.render(opt.items);
+    return view.autopad(opt);
+  };
+    
+  return view;
+})();
+
+// headless view constructor factory
+// takes definitions from parsed specification as input
+// returns a view constructor
+vg.headless.View.Factory = function(defs) {
+  return function(opt) {
+    opt = opt || {};
+    var w = defs.width,
+        h = defs.height,
+        p = defs.padding,
+        r = opt.renderer || "canvas",
+        v = new vg.headless.View(w, h, p, r).defs(defs);
+    if (defs.data.load) v.data(defs.data.load);
+    if (opt.data) v.data(opt.data);
+    return v;
+  };
+};vg.headless.render = function(opt, callback) {
+  function draw(chart) {
+    try {
+      // create and render view
+      var view = chart({
+        data: opt.data,
+        renderer: opt.renderer
+      }).update();
+
+      if (opt.renderer === "svg") {
+        // extract rendered svg
+        callback(null, {svg: view.svg()});
+      } else {
+        // extract rendered canvas, waiting for any images to load
+        view.canvasAsync(function(canvas) {
+          callback(null, {canvas: canvas});
+        });
+      }
+    } catch (err) {
+      callback(err, null);
+    }
+  }
+
+  vg.parse.spec(opt.spec, draw, vg.headless.View.Factory);
+};  return vg;
+})(d3, typeof topojson === "undefined" ? null : topojson);
+// assumes D3 and topojson in global namespace