<p> (function(){if (!Date.now) Date.now = function() {
  return +new Date;
};
try {
  document.createElement("div").style.setProperty("opacity", 0, "");
} catch (error) {
  var d3_style_prototype = CSSStyleDeclaration.prototype,
      d3_style_setProperty = d3_style_prototype.setProperty;
  d3_style_prototype.setProperty = function(name, value, priority) {
    d3_style_setProperty.call(this, name, value + "", priority);
  };
}
d3 = {version: "2.9.1"}; // semver
function d3_class(ctor, properties) {
  try {
    for (var key in properties) {
      Object.defineProperty(ctor.prototype, key, {
        value: properties[key],
        enumerable: false
      });
    }
  } catch (e) {
    ctor.prototype = properties;
  }
}
var d3_array = d3_arraySlice; // conversion for NodeLists

function d3_arrayCopy(pseudoarray) {
  var i = -1, n = pseudoarray.length, array = [];
  while (++i  b ? 1 : a &gt;= b ? 0 : NaN;
};
d3.descending = function(a, b) {
  return b  a ? 1 : b &gt;= a ? 0 : NaN;
};
d3.mean = function(array, f) {
  var n = array.length,
      a,
      m = 0,
      i = -1,
      j = 0;
  if (arguments.length === 1) {
    while (++i  1) array = array.map(f);
  array = array.filter(d3_number);
  return array.length ? d3.quantile(array.sort(d3.ascending), .5) : undefined;
};
d3.min = function(array, f) {
  var i = -1,
      n = array.length,
      a,
      b;
  if (arguments.length === 1) {
    while (++i  b) a = b;
  } else {
    while (++i  b) a = b;
  }
  return a;
};
d3.max = function(array, f) {
  var i = -1,
      n = array.length,
      a,
      b;
  if (arguments.length === 1) {
    while (++i  a) a = b;
  } else {
    while (++i  a) a = b;
  }
  return a;
};
d3.extent = function(array, f) {
  var i = -1,
      n = array.length,
      a,
      b,
      c;
  if (arguments.length === 1) {
    while (++i  b) a = b;
      if (c  b) a = b;
      if (c  1);
      return mean + deviation * x * Math.sqrt(-2 * Math.log(r) / r);
    };
  }
};
function d3_number(x) {
  return x != null &amp;&amp; !isNaN(x);
}
d3.sum = function(array, f) {
  var s = 0,
      n = array.length,
      a,
      i = -1;

  if (arguments.length === 1) {
    while (++i 
d3.quantile = function(values, p) {
  var H = (values.length - 1) * p + 1,
      h = Math.floor(H),
      v = values[h - 1],
      e = H - h;
  return e ? v + e * (values[h] - v) : v;
};
d3.transpose = function(matrix) {
  return d3.zip.apply(d3, matrix);
};
d3.zip = function() {
  if (!(n = arguments.length)) return [];
  for (var i = -1, m = d3.min(arguments, d3_zipLength), zips = new Array(m); ++i &gt; 1;
        if (f.call(a, a[mid], mid) &gt; 1;
        if (x  0) {
      a = b;
    }
  }
  return a;
};
d3.last = function(array, f) {
  var i = 0,
      n = array.length,
      a = array[0],
      b;
  if (arguments.length === 1) f = d3.ascending;
  while (++i = keys.length) return rollup
        ? rollup.call(nest, array) : (sortValues
        ? array.sort(sortValues)
        : array);

    var i = -1,
        n = array.length,
        key = keys[depth++],
        keyValue,
        object,
        valuesByKey = new d3_Map,
        values,
        o = {};

    while (++i = keys.length) return map;

    var a = [],
        sortKey = sortKeys[depth++],
        key;

    for (key in map) {
      a.push({key: key, values: entries(map[key], depth)});
    }

    if (sortKey) a.sort(function(a, b) {
      return sortKey(a.key, b.key);
    });

    return a;
  }

  nest.map = function(array) {
    return map(array, 0);
  };

  nest.entries = function(array) {
    return entries(map(array, 0), 0);
  };

  nest.key = function(d) {
    keys.push(d);
    return nest;
  };

  // Specifies the order for the most-recently specified key.
  // Note: only applies to entries. Map keys are unordered!
  nest.sortKeys = function(order) {
    sortKeys[keys.length - 1] = order;
    return nest;
  };

  // Specifies the order for leaf values.
  // Applies to both maps and entries array.
  nest.sortValues = function(order) {
    sortValues = order;
    return nest;
  };

  nest.rollup = function(f) {
    rollup = f;
    return nest;
  };

  return nest;
};
d3.keys = function(map) {
  var keys = [];
  for (var key in map) keys.push(key);
  return keys;
};
d3.values = function(map) {
  var values = [];
  for (var key in map) values.push(map[key]);
  return values;
};
d3.entries = function(map) {
  var entries = [];
  for (var key in map) entries.push({key: key, value: map[key]});
  return entries;
};
d3.permute = function(array, indexes) {
  var permutes = [],
      i = -1,
      n = indexes.length;
  while (++i  stop) range.push(j / k);
  else while ((j = start + step * ++i) = 200 &amp;&amp; s = 0) {
      prefix = name.substring(0, i);
      name = name.substring(i + 1);
    }
    return d3_nsPrefix.hasOwnProperty(prefix)
        ? {space: d3_nsPrefix[prefix], local: name}
        : name;
  }
};
d3.dispatch = function() {
  var dispatch = new d3_dispatch,
      i = -1,
      n = arguments.length;
  while (++i  0) {
    name = type.substring(i + 1);
    type = type.substring(0, i);
  }

  return arguments.length =^]))?([+\- ])?(#)?(0)?([0-9]+)?(,)?(\.[0-9]+)?([a-zA-Z%])?/;

var d3_format_types = d3.map({
  g: function(x, p) { return x.toPrecision(p); },
  e: function(x, p) { return x.toExponential(p); },
  f: function(x, p) { return x.toFixed(p); },
  r: function(x, p) { return d3.round(x, p = d3_format_precision(x, p)).toFixed(Math.max(0, Math.min(20, p))); }
});

function d3_format_precision(x, p) {
  return p - (x ? 1 + Math.floor(Math.log(x + Math.pow(10, 1 + Math.floor(Math.log(x) / Math.LN10) - p)) / Math.LN10) : 1);
}

function d3_format_typeDefault(x) {
  return x + "";
}

// Apply comma grouping for thousands.
function d3_format_group(value) {
  var i = value.lastIndexOf("."),
      f = i &gt;= 0 ? value.substring(i) : (i = value.length, ""),
      t = [];
  while (i &gt; 0) t.push(value.substring(i -= 3, i + 3));
  return t.reverse().join(",") + f;
}
var d3_formatPrefixes = ["y","z","a","f","p","n","μ","m","","k","M","G","T","P","E","Z","Y"].map(d3_formatPrefix);

d3.formatPrefix = function(value, precision) {
  var i = 0;
  if (value) {
    if (value = 0 ? name.substring(0, i) : name,
      m = i &gt;= 0 ? name.substring(i + 1) : "in";
  t = d3_ease.get(t) || d3_ease_default;
  m = d3_ease_mode.get(m) || d3_ease_identity;
  return d3_ease_clamp(m(t.apply(null, Array.prototype.slice.call(arguments, 1))));
};

function d3_ease_clamp(f) {
  return function(t) {
    return t = 1 ? 1 : f(t);
  };
}

function d3_ease_reverse(f) {
  return function(t) {
    return 1 - f(1 - t);
  };
}

function d3_ease_reflect(f) {
  return function(t) {
    return .5 * (t = 0 &amp;&amp; !(f = d3.interpolators[i](a, b)));
  return f;
};

d3.interpolateNumber = function(a, b) {
  b -= a;
  return function(t) { return a + b * t; };
};

d3.interpolateRound = function(a, b) {
  b -= a;
  return function(t) { return Math.round(a + b * t); };
};

d3.interpolateString = function(a, b) {
  var m, // current match
      i, // current index
      j, // current index (for coallescing)
      s0 = 0, // start index of current string prefix
      s1 = 0, // end index of current string prefix
      s = [], // string constants and placeholders
      q = [], // number interpolators
      n, // q.length
      o;

  // Reset our regular expression!
  d3_interpolate_number.lastIndex = 0;

  // Find all numbers in b.
  for (i = 0; m = d3_interpolate_number.exec(b); ++i) {
    if (m.index) s.push(b.substring(s0, s1 = m.index));
    q.push({i: s.length, x: m[0]});
    s.push(null);
    s0 = d3_interpolate_number.lastIndex;
  }
  if (s0  1 ? 1 : s;
  l = l  1 ? 1 : l;

  /* From FvD 13.37, CSS Color Module Level 3 */
  m2 = l  360) h -= 360;
    else if (h  1) {
    while (++i = 0;) {
      if (node = group[i]) {
        if (next &amp;&amp; next !== node.nextSibling) next.parentNode.insertBefore(node, next);
        next = node;
      }
    }
  }
  return this;
};
d3_selectionPrototype.sort = function(comparator) {
  comparator = d3_selection_sortComparator.apply(this, arguments);
  for (var j = -1, m = this.length; ++j  0) type = type.substring(0, i);

  // if called with only one argument, return the current listener
  if (arguments.length  id) return stop();
        lock.active = id;

        tweens.forEach(function(key, value) {
          if (value = value.call(node, d, i)) {
            tweened.push(value);
          }
        });

        event.start.call(node, d, i);
        if (!tick(elapsed)) d3.timer(tick, 0, time);
        return 1;
      }

      function tick(elapsed) {
        if (lock.active !== id) return stop();

        var t = (elapsed - delay) / duration,
            e = ease(t),
            n = tweened.length;

        while (n &gt; 0) {
          tweened[--n].call(node, e);
        }

        if (t &gt;= 1) {
          stop();
          d3_transitionId = id;
          event.end.call(node, d, i);
          d3_transitionId = 0;
          return 1;
        }
      }

      function stop() {
        if (!--lock.count) delete node.__transition__;
        return 1;
      }
    });
    return 1;
  }, 0, time);

  return groups;
}

var d3_transitionRemove = {};

function d3_transitionNull(d, i, a) {
  return a != "" &amp;&amp; d3_transitionRemove;
}

function d3_transitionTween(name, b) {
  var interpolate = d3_interpolateByName(name);

  function transitionFunction(d, i, a) {
    var v = b.call(this, d, i);
    return v == null
        ? a != "" &amp;&amp; d3_transitionRemove
        : a != v &amp;&amp; interpolate(a, v);
  }

  function transitionString(d, i, a) {
    return a != b &amp;&amp; interpolate(a, b);
  }

  return typeof b === "function" ? transitionFunction
      : b == null ? d3_transitionNull
      : (b += "", transitionString);
}

var d3_transitionPrototype = [],
    d3_transitionNextId = 0,
    d3_transitionId = 0,
    d3_transitionDefaultDelay = 0,
    d3_transitionDefaultDuration = 250,
    d3_transitionDefaultEase = d3.ease("cubic-in-out"),
    d3_transitionDelay = d3_transitionDefaultDelay,
    d3_transitionDuration = d3_transitionDefaultDuration,
    d3_transitionEase = d3_transitionDefaultEase;

d3_transitionPrototype.call = d3_selectionPrototype.call;

d3.transition = function(selection) {
  return arguments.length
      ? (d3_transitionId ? selection.transition() : selection)
      : d3_selectionRoot.transition();
};

d3.transition.prototype = d3_transitionPrototype;
d3_transitionPrototype.select = function(selector) {
  var subgroups = [],
      subgroup,
      subnode,
      node;

  if (typeof selector !== "function") selector = d3_selection_selector(selector);

  for (var j = -1, m = this.length; ++j = t1.delay) t1.flush = t1.callback(elapsed);
    t1 = t1.next;
  }

  var delay = d3_timer_flush() - now;
  if (delay &gt; 24) {
    if (isFinite(delay)) {
      clearTimeout(d3_timer_timeout);
      d3_timer_timeout = setTimeout(d3_timer_step, delay);
    }
    d3_timer_interval = 0;
  } else {
    d3_timer_interval = 1;
    d3_timer_frame(d3_timer_step);
  }
}

d3.timer.flush = function() {
  var elapsed,
      now = Date.now(),
      t1 = d3_timer_queue;

  while (t1) {
    elapsed = now - t1.then;
    if (!t1.delay) t1.flush = t1.callback(elapsed);
    t1 = t1.next;
  }

  d3_timer_flush();
};

// Flush after callbacks, to avoid concurrent queue modification.
function d3_timer_flush() {
  var t0 = null,
      t1 = d3_timer_queue,
      then = Infinity;
  while (t1) {
    if (t1.flush) {
      t1 = t0 ? t0.next = t1.next : d3_timer_queue = t1.next;
    } else {
      then = Math.min(then, t1.then + t1.delay);
      t1 = (t0 = t1).next;
    }
  }
  return then;
}

var d3_timer_frame = window.requestAnimationFrame
    || window.webkitRequestAnimationFrame
    || window.mozRequestAnimationFrame
    || window.oRequestAnimationFrame
    || window.msRequestAnimationFrame
    || function(callback) { setTimeout(callback, 17); };
d3.transform = function(string) {
  var g = document.createElementNS(d3.ns.prefix.svg, "g"),
      identity = {a: 1, b: 0, c: 0, d: 1, e: 0, f: 0};
  return (d3.transform = function(string) {
    g.setAttribute("transform", string);
    var t = g.transform.baseVal.consolidate();
    return new d3_transform(t ? t.matrix : identity);
  })(string);
};

// Compute x-scale and normalize the first row.
// Compute shear and make second row orthogonal to first.
// Compute y-scale and normalize the second row.
// Finally, compute the rotation.
function d3_transform(m) {
  var r0 = [m.a, m.b],
      r1 = [m.c, m.d],
      kx = d3_transformNormalize(r0),
      kz = d3_transformDot(r0, r1),
      ky = d3_transformNormalize(d3_transformCombine(r1, r0, -kz)) || 0;
  if (r0[0] * r1[1]  2 ? d3_scale_polylinear : d3_scale_bilinear,
        uninterpolate = clamp ? d3_uninterpolateClamp : d3_uninterpolateNumber;
    output = linear(domain, range, uninterpolate, interpolate);
    input = linear(range, domain, uninterpolate, d3.interpolate);
    return scale;
  }

  function scale(x) {
    return output(x);
  }

  // Note: requires range is coercible to number!
  scale.invert = function(y) {
    return input(y);
  };

  scale.domain = function(x) {
    if (!arguments.length) return domain;
    domain = x.map(Number);
    return rescale();
  };

  scale.range = function(x) {
    if (!arguments.length) return range;
    range = x;
    return rescale();
  };

  scale.rangeRound = function(x) {
    return scale.range(x).interpolate(d3.interpolateRound);
  };

  scale.clamp = function(x) {
    if (!arguments.length) return clamp;
    clamp = x;
    return rescale();
  };

  scale.interpolate = function(x) {
    if (!arguments.length) return interpolate;
    interpolate = x;
    return rescale();
  };

  scale.ticks = function(m) {
    return d3_scale_linearTicks(domain, m);
  };

  scale.tickFormat = function(m) {
    return d3_scale_linearTickFormat(domain, m);
  };

  scale.nice = function() {
    d3_scale_nice(domain, d3_scale_linearNice);
    return rescale();
  };

  scale.copy = function() {
    return d3_scale_linear(domain, range, interpolate, clamp);
  };

  return rescale();
}

function d3_scale_linearRebind(scale, linear) {
  return d3.rebind(scale, linear, "range", "rangeRound", "interpolate", "clamp");
}

function d3_scale_linearNice(dx) {
  dx = Math.pow(10, Math.round(Math.log(dx) / Math.LN10) - 1);
  return {
    floor: function(x) { return Math.floor(x / dx) * dx; },
    ceil: function(x) { return Math.ceil(x / dx) * dx; }
  };
}

function d3_scale_linearTickRange(domain, m) {
  var extent = d3_scaleExtent(domain),
      span = extent[1] - extent[0],
      step = Math.pow(10, Math.floor(Math.log(span / m) / Math.LN10)),
      err = m / span * step;

  // Filter ticks to get closer to the desired count.
  if (err  0; k--) ticks.push(pow(i) * k);
      } else {
        for (; i  v; j--) {} // strip big values
      ticks = ticks.slice(i, j);
    }
    return ticks;
  };

  scale.tickFormat = function(n, format) {
    if (arguments.length  0 ? 0 : -x) / Math.LN10;
}

d3_scale_logp.pow = function(x) {
  return Math.pow(10, x);
};

d3_scale_logn.pow = function(x) {
  return -Math.pow(10, -x);
};
d3.scale.pow = function() {
  return d3_scale_pow(d3.scale.linear(), 1);
};

function d3_scale_pow(linear, exponent) {
  var powp = d3_scale_powPow(exponent),
      powb = d3_scale_powPow(1 / exponent);

  function scale(x) {
    return linear(powp(x));
  }

  scale.invert = function(x) {
    return powb(linear.invert(x));
  };

  scale.domain = function(x) {
    if (!arguments.length) return linear.domain().map(powb);
    linear.domain(x.map(powp));
    return scale;
  };

  scale.ticks = function(m) {
    return d3_scale_linearTicks(scale.domain(), m);
  };

  scale.tickFormat = function(m) {
    return d3_scale_linearTickFormat(scale.domain(), m);
  };

  scale.nice = function() {
    return scale.domain(d3_scale_nice(scale.domain(), d3_scale_linearNice));
  };

  scale.exponent = function(x) {
    if (!arguments.length) return exponent;
    var domain = scale.domain();
    powp = d3_scale_powPow(exponent = x);
    powb = d3_scale_powPow(1 / exponent);
    return scale.domain(domain);
  };

  scale.copy = function() {
    return d3_scale_pow(linear.copy(), exponent);
  };

  return d3_scale_linearRebind(scale, linear);
}

function d3_scale_powPow(e) {
  return function(x) {
    return x = d3_svg_arcMax
      ? (r0
      ? "M0," + r1
      + "A" + r1 + "," + r1 + " 0 1,1 0," + (-r1)
      + "A" + r1 + "," + r1 + " 0 1,1 0," + r1
      + "M0," + r0
      + "A" + r0 + "," + r0 + " 0 1,0 0," + (-r0)
      + "A" + r0 + "," + r0 + " 0 1,0 0," + r0
      + "Z"
      : "M0," + r1
      + "A" + r1 + "," + r1 + " 0 1,1 0," + (-r1)
      + "A" + r1 + "," + r1 + " 0 1,1 0," + r1
      + "Z")
      : (r0
      ? "M" + r1 * c0 + "," + r1 * s0
      + "A" + r1 + "," + r1 + " 0 " + df + ",1 " + r1 * c1 + "," + r1 * s1
      + "L" + r0 * c1 + "," + r0 * s1
      + "A" + r0 + "," + r0 + " 0 " + df + ",0 " + r0 * c0 + "," + r0 * s0
      + "Z"
      : "M" + r1 * c0 + "," + r1 * s0
      + "A" + r1 + "," + r1 + " 0 " + df + ",1 " + r1 * c1 + "," + r1 * s1
      + "L0,0"
      + "Z");
  }

  arc.innerRadius = function(v) {
    if (!arguments.length) return innerRadius;
    innerRadius = d3_functor(v);
    return arc;
  };

  arc.outerRadius = function(v) {
    if (!arguments.length) return outerRadius;
    outerRadius = d3_functor(v);
    return arc;
  };

  arc.startAngle = function(v) {
    if (!arguments.length) return startAngle;
    startAngle = d3_functor(v);
    return arc;
  };

  arc.endAngle = function(v) {
    if (!arguments.length) return endAngle;
    endAngle = d3_functor(v);
    return arc;
  };

  arc.centroid = function() {
    var r = (innerRadius.apply(this, arguments)
        + outerRadius.apply(this, arguments)) / 2,
        a = (startAngle.apply(this, arguments)
        + endAngle.apply(this, arguments)) / 2 + d3_svg_arcOffset;
    return [Math.cos(a) * r, Math.sin(a) * r];
  };

  return arc;
};

var d3_svg_arcOffset = -Math.PI / 2,
    d3_svg_arcMax = 2 * Math.PI - 1e-6;

function d3_svg_arcInnerRadius(d) {
  return d.innerRadius;
}

function d3_svg_arcOuterRadius(d) {
  return d.outerRadius;
}

function d3_svg_arcStartAngle(d) {
  return d.startAngle;
}

function d3_svg_arcEndAngle(d) {
  return d.endAngle;
}
function d3_svg_line(projection) {
  var x = d3_svg_lineX,
      y = d3_svg_lineY,
      defined = d3_true,
      interpolate = d3_svg_lineInterpolatorDefault,
      interpolator = d3_svg_lineLinear,
      tension = .7;

  function line(data) {
    var segments = [],
        points = [],
        i = -1,
        n = data.length,
        d,
        fx = d3_functor(x),
        fy = d3_functor(y);

    function segment() {
      segments.push("M", interpolator(projection(points), tension));
    }

    while (++i  1) {
    t = tangents[1];
    p = points[pi];
    pi++;
    path += "C" + (p0[0] + t0[0]) + "," + (p0[1] + t0[1])
        + "," + (p[0] - t[0]) + "," + (p[1] - t[1])
        + "," + p[0] + "," + p[1];
    for (var i = 2; i  to a circle of radius 3.
      s = a * a + b * b;
      if (s &gt; 9) {
        s = d * 3 / Math.sqrt(s);
        m[i] = s * a;
        m[i + 1] = s * b;
      }
    }
  }

  // Compute the normalized tangent vector from the slopes. Note that if x is
  // not monotonic, it's possible that the slope will be infinite, so we protect
  // against NaN by setting the coordinate to zero.
  i = -1; while (++i  Math.PI) + ",1 " + p;
  }

  function curve(r0, p0, r1, p1) {
    return "Q 0,0 " + p1;
  }

  chord.radius = function(v) {
    if (!arguments.length) return radius;
    radius = d3_functor(v);
    return chord;
  };

  chord.source = function(v) {
    if (!arguments.length) return source;
    source = d3_functor(v);
    return chord;
  };

  chord.target = function(v) {
    if (!arguments.length) return target;
    target = d3_functor(v);
    return chord;
  };

  chord.startAngle = function(v) {
    if (!arguments.length) return startAngle;
    startAngle = d3_functor(v);
    return chord;
  };

  chord.endAngle = function(v) {
    if (!arguments.length) return endAngle;
    endAngle = d3_functor(v);
    return chord;
  };

  return chord;
};

function d3_svg_chordSource(d) {
  return d.source;
}

function d3_svg_chordTarget(d) {
  return d.target;
}

function d3_svg_chordRadius(d) {
  return d.radius;
}

function d3_svg_chordStartAngle(d) {
  return d.startAngle;
}

function d3_svg_chordEndAngle(d) {
  return d.endAngle;
}
d3.svg.diagonal = function() {
  var source = d3_svg_chordSource,
      target = d3_svg_chordTarget,
      projection = d3_svg_diagonalProjection;

  function diagonal(d, i) {
    var p0 = source.call(this, d, i),
        p3 = target.call(this, d, i),
        m = (p0.y + p3.y) / 2,
        p = [p0, {x: p0.x, y: m}, {x: p3.x, y: m}, p3];
    p = p.map(projection);
    return "M" + p[0] + "C" + p[1] + " " + p[2] + " " + p[3];
  }

  diagonal.source = function(x) {
    if (!arguments.length) return source;
    source = d3_functor(x);
    return diagonal;
  };

  diagonal.target = function(x) {
    if (!arguments.length) return target;
    target = d3_functor(x);
    return diagonal;
  };

  diagonal.projection = function(x) {
    if (!arguments.length) return projection;
    projection = x;
    return diagonal;
  };

  return diagonal;
};

function d3_svg_diagonalProjection(d) {
  return [d.x, d.y];
}
d3.svg.diagonal.radial = function() {
  var diagonal = d3.svg.diagonal(),
      projection = d3_svg_diagonalProjection,
      projection_ = diagonal.projection;

  diagonal.projection = function(x) {
    return arguments.length
        ? projection_(d3_svg_diagonalRadialProjection(projection = x))
        : projection;
  };

  return diagonal;
};

function d3_svg_diagonalRadialProjection(projection) {
  return function() {
    var d = projection.apply(this, arguments),
        r = d[0],
        a = d[1] + d3_svg_arcOffset;
    return [r * Math.cos(a), r * Math.sin(a)];
  };
}
d3.svg.mouse = d3.mouse;
d3.svg.touches = d3.touches;
d3.svg.symbol = function() {
  var type = d3_svg_symbolType,
      size = d3_svg_symbolSize;

  function symbol(d, i) {
    return (d3_svg_symbols.get(type.call(this, d, i))
        || d3_svg_symbolCircle)
        (size.call(this, d, i));
  }

  symbol.type = function(x) {
    if (!arguments.length) return type;
    type = d3_functor(x);
    return symbol;
  };

  // size of symbol in square pixels
  symbol.size = function(x) {
    if (!arguments.length) return size;
    size = d3_functor(x);
    return symbol;
  };

  return symbol;
};

function d3_svg_symbolSize() {
  return 64;
}

function d3_svg_symbolType() {
  return "circle";
}

function d3_svg_symbolCircle(size) {
  var r = Math.sqrt(size / Math.PI);
  return "M0," + r
      + "A" + r + "," + r + " 0 1,1 0," + (-r)
      + "A" + r + "," + r + " 0 1,1 0," + r
      + "Z";
}

// TODO cross-diagonal?
var d3_svg_symbols = d3.map({
  "circle": d3_svg_symbolCircle,
  "cross": function(size) {
    var r = Math.sqrt(size / 5) / 2;
    return "M" + -3 * r + "," + -r
        + "H" + -r
        + "V" + -3 * r
        + "H" + r
        + "V" + -r
        + "H" + 3 * r
        + "V" + r
        + "H" + r
        + "V" + 3 * r
        + "H" + -r
        + "V" + r
        + "H" + -3 * r
        + "Z";
  },
  "diamond": function(size) {
    var ry = Math.sqrt(size / (2 * d3_svg_symbolTan30)),
        rx = ry * d3_svg_symbolTan30;
    return "M0," + -ry
        + "L" + rx + ",0"
        + " 0," + ry
        + " " + -rx + ",0"
        + "Z";
  },
  "square": function(size) {
    var r = Math.sqrt(size) / 2;
    return "M" + -r + "," + -r
        + "L" + r + "," + -r
        + " " + r + "," + r
        + " " + -r + "," + r
        + "Z";
  },
  "triangle-down": function(size) {
    var rx = Math.sqrt(size / d3_svg_symbolSqrt3),
        ry = rx * d3_svg_symbolSqrt3 / 2;
    return "M0," + ry
        + "L" + rx +"," + -ry
        + " " + -rx + "," + -ry
        + "Z";
  },
  "triangle-up": function(size) {
    var rx = Math.sqrt(size / d3_svg_symbolSqrt3),
        ry = rx * d3_svg_symbolSqrt3 / 2;
    return "M0," + -ry
        + "L" + rx +"," + ry
        + " " + -rx + "," + ry
        + "Z";
  }
});

d3.svg.symbolTypes = d3_svg_symbols.keys();

var d3_svg_symbolSqrt3 = Math.sqrt(3),
    d3_svg_symbolTan30 = Math.tan(30 * Math.PI / 180);
d3.svg.axis = function() {
  var scale = d3.scale.linear(),
      orient = "bottom",
      tickMajorSize = 6,
      tickMinorSize = 6,
      tickEndSize = 6,
      tickPadding = 3,
      tickArguments_ = [10],
      tickValues = null,
      tickFormat_,
      tickSubdivide = 0;

  function axis(g) {
    g.each(function() {
      var g = d3.select(this);

      // Ticks, or domain values for ordinal scales.
      var ticks = tickValues == null ? (scale.ticks ? scale.ticks.apply(scale, tickArguments_) : scale.domain()) : tickValues,
          tickFormat = tickFormat_ == null ? (scale.tickFormat ? scale.tickFormat.apply(scale, tickArguments_) : String) : tickFormat_;

      // Minor ticks.
      var subticks = d3_svg_axisSubdivide(scale, ticks, tickSubdivide),
          subtick = g.selectAll(".minor").data(subticks, String),
          subtickEnter = subtick.enter().insert("line", "g").attr("class", "tick minor").style("opacity", 1e-6),
          subtickExit = d3.transition(subtick.exit()).style("opacity", 1e-6).remove(),
          subtickUpdate = d3.transition(subtick).style("opacity", 1);

      // Major ticks.
      var tick = g.selectAll("g").data(ticks, String),
          tickEnter = tick.enter().insert("g", "path").style("opacity", 1e-6),
          tickExit = d3.transition(tick.exit()).style("opacity", 1e-6).remove(),
          tickUpdate = d3.transition(tick).style("opacity", 1),
          tickTransform;

      // Domain.
      var range = d3_scaleRange(scale),
          path = g.selectAll(".domain").data([0]),
          pathEnter = path.enter().append("path").attr("class", "domain"),
          pathUpdate = d3.transition(path);

      // Stash a snapshot of the new scale, and retrieve the old snapshot.
      var scale1 = scale.copy(),
          scale0 = this.__chart__ || scale1;
      this.__chart__ = scale1;

      tickEnter.append("line").attr("class", "tick");
      tickEnter.append("text");
      tickUpdate.select("text").text(tickFormat);

      switch (orient) {
        case "bottom": {
          tickTransform = d3_svg_axisX;
          subtickEnter.attr("y2", tickMinorSize);
          subtickUpdate.attr("x2", 0).attr("y2", tickMinorSize);
          tickEnter.select("line").attr("y2", tickMajorSize);
          tickEnter.select("text").attr("y", Math.max(tickMajorSize, 0) + tickPadding);
          tickUpdate.select("line").attr("x2", 0).attr("y2", tickMajorSize);
          tickUpdate.select("text").attr("x", 0).attr("y", Math.max(tickMajorSize, 0) + tickPadding).attr("dy", ".71em").attr("text-anchor", "middle");
          pathUpdate.attr("d", "M" + range[0] + "," + tickEndSize + "V0H" + range[1] + "V" + tickEndSize);
          break;
        }
        case "top": {
          tickTransform = d3_svg_axisX;
          subtickEnter.attr("y2", -tickMinorSize);
          subtickUpdate.attr("x2", 0).attr("y2", -tickMinorSize);
          tickEnter.select("line").attr("y2", -tickMajorSize);
          tickEnter.select("text").attr("y", -(Math.max(tickMajorSize, 0) + tickPadding));
          tickUpdate.select("line").attr("x2", 0).attr("y2", -tickMajorSize);
          tickUpdate.select("text").attr("x", 0).attr("y", -(Math.max(tickMajorSize, 0) + tickPadding)).attr("dy", "0em").attr("text-anchor", "middle");
          pathUpdate.attr("d", "M" + range[0] + "," + -tickEndSize + "V0H" + range[1] + "V" + -tickEndSize);
          break;
        }
        case "left": {
          tickTransform = d3_svg_axisY;
          subtickEnter.attr("x2", -tickMinorSize);
          subtickUpdate.attr("x2", -tickMinorSize).attr("y2", 0);
          tickEnter.select("line").attr("x2", -tickMajorSize);
          tickEnter.select("text").attr("x", -(Math.max(tickMajorSize, 0) + tickPadding));
          tickUpdate.select("line").attr("x2", -tickMajorSize).attr("y2", 0);
          tickUpdate.select("text").attr("x", -(Math.max(tickMajorSize, 0) + tickPadding)).attr("y", 0).attr("dy", ".32em").attr("text-anchor", "end");
          pathUpdate.attr("d", "M" + -tickEndSize + "," + range[0] + "H0V" + range[1] + "H" + -tickEndSize);
          break;
        }
        case "right": {
          tickTransform = d3_svg_axisY;
          subtickEnter.attr("x2", tickMinorSize);
          subtickUpdate.attr("x2", tickMinorSize).attr("y2", 0);
          tickEnter.select("line").attr("x2", tickMajorSize);
          tickEnter.select("text").attr("x", Math.max(tickMajorSize, 0) + tickPadding);
          tickUpdate.select("line").attr("x2", tickMajorSize).attr("y2", 0);
          tickUpdate.select("text").attr("x", Math.max(tickMajorSize, 0) + tickPadding).attr("y", 0).attr("dy", ".32em").attr("text-anchor", "start");
          pathUpdate.attr("d", "M" + tickEndSize + "," + range[0] + "H0V" + range[1] + "H" + tickEndSize);
          break;
        }
      }

      // For quantitative scales:
      // - enter new ticks from the old scale
      // - exit old ticks to the new scale
      if (scale.ticks) {
        tickEnter.call(tickTransform, scale0);
        tickUpdate.call(tickTransform, scale1);
        tickExit.call(tickTransform, scale1);
        subtickEnter.call(tickTransform, scale0);
        subtickUpdate.call(tickTransform, scale1);
        subtickExit.call(tickTransform, scale1);
      }

      // For ordinal scales:
      // - any entering ticks are undefined in the old scale
      // - any exiting ticks are undefined in the new scale
      // Therefore, we only need to transition updating ticks.
      else {
        var dx = scale1.rangeBand() / 2, x = function(d) { return scale1(d) + dx; };
        tickEnter.call(tickTransform, x);
        tickUpdate.call(tickTransform, x);
      }
    });
  }

  axis.scale = function(x) {
    if (!arguments.length) return scale;
    scale = x;
    return axis;
  };

  axis.orient = function(x) {
    if (!arguments.length) return orient;
    orient = x;
    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, z) {
    if (!arguments.length) return tickMajorSize;
    var n = arguments.length - 1;
    tickMajorSize = +x;
    tickMinorSize = n &gt; 1 ? +y : tickMajorSize;
    tickEndSize = n &gt; 0 ? +arguments[n] : tickMajorSize;
    return axis;
  };

  axis.tickPadding = function(x) {
    if (!arguments.length) return tickPadding;
    tickPadding = +x;
    return axis;
  };

  axis.tickSubdivide = function(x) {
    if (!arguments.length) return tickSubdivide;
    tickSubdivide = +x;
    return axis;
  };

  return axis;
};

function d3_svg_axisX(selection, x) {
  selection.attr("transform", function(d) { return "translate(" + x(d) + ",0)"; });
}

function d3_svg_axisY(selection, y) {
  selection.attr("transform", function(d) { return "translate(0," + y(d) + ")"; });
}

function d3_svg_axisSubdivide(scale, ticks, m) {
  subticks = [];
  if (m &amp;&amp; ticks.length &gt; 1) {
    var extent = d3_scaleExtent(scale.domain()),
        subticks,
        i = -1,
        n = ticks.length,
        d = (ticks[1] - ticks[0]) / ++m,
        j,
        v;
    while (++i  0;) {
        if ((v = +ticks[i] - j * d) &gt;= extent[0]) {
          subticks.push(v);
        }
      }
    }
    for (--i, j = 0; ++j rect,.s&gt;rect").attr("width", extent[1][0] - extent[0][0]);
  }

  function redrawY(g) {
    g.select(".extent").attr("y", extent[0][1]);
    g.selectAll(".extent,.e&gt;rect,.w&gt;rect").attr("height", extent[1][1] - extent[0][1]);
  }

  function brushstart() {
    var target = this,
        eventTarget = d3.select(d3.event.target),
        event_ = event.of(target, arguments),
        g = d3.select(target),
        resizing = eventTarget.datum(),
        resizingX = !/^(n|s)$/.test(resizing) &amp;&amp; x,
        resizingY = !/^(e|w)$/.test(resizing) &amp;&amp; y,
        dragging = eventTarget.classed("extent"),
        center,
        origin = mouse(),
        offset;

    var w = d3.select(window)
        .on("mousemove.brush", brushmove)
        .on("mouseup.brush", brushend)
        .on("touchmove.brush", brushmove)
        .on("touchend.brush", brushend)
        .on("keydown.brush", keydown)
        .on("keyup.brush", keyup);

    // If the extent was clicked on, drag rather than brush;
    // store the point between the mouse and extent origin instead.
    if (dragging) {
      origin[0] = extent[0][0] - origin[0];
      origin[1] = extent[0][1] - origin[1];
    }

    // If a resizer was clicked on, record which side is to be resized.
    // Also, set the origin to the opposite side.
    else if (resizing) {
      var ex = +/w$/.test(resizing),
          ey = +/^n/.test(resizing);
      offset = [extent[1 - ex][0] - origin[0], extent[1 - ey][1] - origin[1]];
      origin[0] = extent[ex][0];
      origin[1] = extent[ey][1];
    }

    // If the ALT key is down when starting a brush, the center is at the mouse.
    else if (d3.event.altKey) center = origin.slice();

    // Propagate the active cursor to the body for the drag duration.
    g.style("pointer-events", "none").selectAll(".resize").style("display", null);
    d3.select("body").style("cursor", eventTarget.style("cursor"));

    // Notify listeners.
    event_({type: "brushstart"});
    brushmove();
    d3_eventCancel();

    function mouse() {
      var touches = d3.event.changedTouches;
      return touches ? d3.touches(target, touches)[0] : d3.mouse(target);
    }

    function keydown() {
      if (d3.event.keyCode == 32) {
        if (!dragging) {
          center = null;
          origin[0] -= extent[1][0];
          origin[1] -= extent[1][1];
          dragging = 2;
        }
        d3_eventCancel();
      }
    }

    function keyup() {
      if (d3.event.keyCode == 32 &amp;&amp; dragging == 2) {
        origin[0] += extent[1][0];
        origin[1] += extent[1][1];
        dragging = 0;
        d3_eventCancel();
      }
    }

    function brushmove() {
      var point = mouse(),
          moved = false;

      // Preserve the offset for thick resizers.
      if (offset) {
        point[0] += offset[0];
        point[1] += offset[1];
      }

      if (!dragging) {

        // If needed, determine the center from the current extent.
        if (d3.event.altKey) {
          if (!center) center = [(extent[0][0] + extent[1][0]) / 2, (extent[0][1] + extent[1][1]) / 2];

          // Update the origin, for when the ALT key is released.
          origin[0] = extent[+(point[0]  0) alpha = x; // we might keep it hot
      else alpha = 0; // or, next tick will dispatch "end"
    } else if (x &gt; 0) { // otherwise, fire it up!
      event.start({type: "start", alpha: alpha = x});
      d3.timer(force.tick);
    }

    return force;
  };

  force.start = function() {
    var i,
        j,
        n = nodes.length,
        m = links.length,
        w = size[0],
        h = size[1],
        neighbors,
        o;

    for (i = 0; i  max) max = o;
      sums.push(o);
    }
    for (j = 0; j  v) {
      j = i;
      v = k;
    }
  }
  return j;
}

function d3_layout_stackReduceSum(d) {
  return d.reduce(d3_layout_stackSum, 0);
}

function d3_layout_stackSum(p, d) {
  return p + d[1];
}
d3.layout.histogram = function() {
  var frequency = true,
      valuer = Number,
      ranger = d3_layout_histogramRange,
      binner = d3_layout_histogramBinSturges;

  function histogram(data, i) {
    var bins = [],
        values = data.map(valuer, this),
        range = ranger.call(this, values, i),
        thresholds = binner.call(this, range, values, i),
        bin,
        i = -1,
        n = values.length,
        m = thresholds.length - 1,
        k = frequency ? 1 : 1 / n,
        x;

    // Initialize the bins.
    while (++i  0) {
      i = -1; while(++i = range[0]) &amp;&amp; (x  .001; // within epsilon
}

function d3_layout_packCircle(nodes) {
  var xMin = Infinity,
      xMax = -Infinity,
      yMin = Infinity,
      yMax = -Infinity,
      n = nodes.length,
      a, b, c, j, k;

  function bound(node) {
    xMin = Math.min(node.x - node.r, xMin);
    xMax = Math.max(node.x + node.r, xMax);
    yMin = Math.min(node.y - node.r, yMin);
    yMax = Math.max(node.y + node.r, yMax);
  }

  // Create node links.
  nodes.forEach(d3_layout_packLink);

  // Create first node.
  a = nodes[0];
  a.x = -a.r;
  a.y = 0;
  bound(a);

  // Create second node.
  if (n &gt; 1) {
    b = nodes[1];
    b.x = b.r;
    b.y = 0;
    bound(b);

    // Create third node and build chain.
    if (n &gt; 2) {
      c = nodes[2];
      d3_layout_packPlace(a, b, c);
      bound(c);
      d3_layout_packInsert(a, c);
      a._pack_prev = c;
      d3_layout_packInsert(c, b);
      b = a._pack_next;

      // Now iterate through the rest.
      for (var i = 3; i  0) {
            d3_layout_treeMove(d3_layout_treeAncestor(vim, node, ancestor), node, shift);
            sip += shift;
            sop += shift;
          }
          sim += vim._tree.mod;
          sip += vip._tree.mod;
          som += vom._tree.mod;
          sop += vop._tree.mod;
        }
        if (vim &amp;&amp; !d3_layout_treeRight(vop)) {
          vop._tree.thread = vim;
          vop._tree.mod += sim - sop;
        }
        if (vip &amp;&amp; !d3_layout_treeLeft(vom)) {
          vom._tree.thread = vip;
          vom._tree.mod += sip - som;
          ancestor = node;
        }
      }
      return ancestor;
    }

    // Initialize temporary layout variables.
    d3_layout_treeVisitAfter(root, function(node, previousSibling) {
      node._tree = {
        ancestor: node,
        prelim: 0,
        mod: 0,
        change: 0,
        shift: 0,
        number: previousSibling ? previousSibling._tree.number + 1 : 0
      };
    });

    // Compute the layout using Buchheim et al.'s algorithm.
    firstWalk(root);
    secondWalk(root, -root._tree.prelim);

    // Compute the left-most, right-most, and depth-most nodes for extents.
    var left = d3_layout_treeSearch(root, d3_layout_treeLeftmost),
        right = d3_layout_treeSearch(root, d3_layout_treeRightmost),
        deep = d3_layout_treeSearch(root, d3_layout_treeDeepest),
        x0 = left.x - separation(left, right) / 2,
        x1 = right.x + separation(right, left) / 2,
        y1 = deep.depth || 1;

    // Clear temporary layout variables; transform x and y.
    d3_layout_treeVisitAfter(root, function(node) {
      node.x = (node.x - x0) / (x1 - x0) * size[0];
      node.y = node.depth / y1 * size[1];
      delete node._tree;
    });

    return nodes;
  }

  tree.separation = function(x) {
    if (!arguments.length) return separation;
    separation = x;
    return tree;
  };

  tree.size = function(x) {
    if (!arguments.length) return size;
    size = x;
    return tree;
  };

  return d3_layout_hierarchyRebind(tree, hierarchy);
};

function d3_layout_treeSeparation(a, b) {
  return a.parent == b.parent ? 1 : 2;
}

// function d3_layout_treeSeparationRadial(a, b) {
//   return (a.parent == b.parent ? 1 : 2) / a.depth;
// }

function d3_layout_treeLeft(node) {
  var children = node.children;
  return children &amp;&amp; children.length ? children[0] : node._tree.thread;
}

function d3_layout_treeRight(node) {
  var children = node.children,
      n;
  return children &amp;&amp; (n = children.length) ? children[n - 1] : node._tree.thread;
}

function d3_layout_treeSearch(node, compare) {
  var children = node.children;
  if (children &amp;&amp; (n = children.length)) {
    var child,
        n,
        i = -1;
    while (++i  0) {
        node = child;
      }
    }
  }
  return node;
}

function d3_layout_treeRightmost(a, b) {
  return a.x - b.x;
}

function d3_layout_treeLeftmost(a, b) {
  return b.x - a.x;
}

function d3_layout_treeDeepest(a, b) {
  return a.depth - b.depth;
}

function d3_layout_treeVisitAfter(node, callback) {
  function visit(node, previousSibling) {
    var children = node.children;
    if (children &amp;&amp; (n = children.length)) {
      var child,
          previousChild = null,
          i = -1,
          n;
      while (++i = 0) {
    child = children[i]._tree;
    child.prelim += shift;
    child.mod += shift;
    shift += child.shift + (change += child.change);
  }
}

function d3_layout_treeMove(ancestor, node, shift) {
  ancestor = ancestor._tree;
  node = node._tree;
  var change = shift / (node.number - ancestor.number);
  ancestor.change += change;
  node.change -= change;
  node.shift += shift;
  node.prelim += shift;
  node.mod += shift;
}

function d3_layout_treeAncestor(vim, node, ancestor) {
  return vim._tree.ancestor.parent == node.parent
      ? vim._tree.ancestor
      : ancestor;
}
// Squarified Treemaps by Mark Bruls, Kees Huizing, and Jarke J. van Wijk
// Modified to support a target aspect ratio by Jeff Heer
d3.layout.treemap = function() {
  var hierarchy = d3.layout.hierarchy(),
      round = Math.round,
      size = [1, 1], // width, height
      padding = null,
      pad = d3_layout_treemapPadNull,
      sticky = false,
      stickies,
      ratio = 0.5 * (1 + Math.sqrt(5)); // golden ratio

  // Compute the area for each child based on value &amp; scale.
  function scale(children, k) {
    var i = -1,
        n = children.length,
        child,
        area;
    while (++i  0) {
        row.push(child = remaining[n - 1]);
        row.area += child.area;
        if ((score = worst(row, u))  rmax) rmax = r;
    }
    s *= s;
    u *= u;
    return s
        ? Math.max((u * rmax * ratio) / s, s / (u * rmin * ratio))
        : Infinity;
  }

  // Positions the specified row of nodes. Modifies `rect`.
  function position(row, u, rect, flush) {
    var i = -1,
        n = row.length,
        x = rect.x,
        y = rect.y,
        v = u ? round(row.area / u) : 0,
        o;
    if (u == rect.dx) { // horizontal subdivision
      if (flush || v &gt; rect.dy) v = rect.dy; // over+underflow
      while (++i  rect.dx) v = rect.dx; // over+underflow
      while (++i = text.length) return EOF; // special case: end of file
    if (eol) { eol = false; return EOL; } // special case: end of line

    // special case: quotes
    var j = re.lastIndex;
    if (text.charCodeAt(j) === 34) {
      var i = j;
      while (i++  50 ? alaska
        : lon  0) {
          path.push("M");
          while (++j  0) {
            path.push("M");
            while (++k  right) right = x;
    if (y  top) top = y;
  });
  return [[left, bottom], [right, top]];
};

function d3_geo_bounds(o, f) {
  if (d3_geo_boundsTypes.hasOwnProperty(o.type)) d3_geo_boundsTypes[o.type](o, f);
}

var d3_geo_boundsTypes = {
  Feature: d3_geo_boundsFeature,
  FeatureCollection: d3_geo_boundsFeatureCollection,
  GeometryCollection: d3_geo_boundsGeometryCollection,
  LineString: d3_geo_boundsLineString,
  MultiLineString: d3_geo_boundsMultiLineString,
  MultiPoint: d3_geo_boundsLineString,
  MultiPolygon: d3_geo_boundsMultiPolygon,
  Point: d3_geo_boundsPoint,
  Polygon: d3_geo_boundsPolygon
};

function d3_geo_boundsFeature(o, f) {
  d3_geo_bounds(o.geometry, f);
}

function d3_geo_boundsFeatureCollection(o, f) {
  for (var a = o.features, i = 0, n = a.length; i marching
 * squares algorithm. Returns the contour polygon as an array of points.
 *
 * @param grid a two-input function(x, y) that returns true for values
 * inside the contour and false for values outside the contour.
 * @param start an optional starting point [x, y] on the grid.
 * @returns polygon [[x1, y1], [x2, y2], …]
 */
d3.geom.contour = function(grid, start) {
  var s = start || d3_geom_contourStart(grid), // starting point
      c = [],    // contour polygon
      x = s[0],  // current x position
      y = s[1],  // current y position
      dx = 0,    // next x direction
      dy = 0,    // next y direction
      pdx = NaN, // previous x direction
      pdy = NaN, // previous y direction
      i = 0;

  do {
    // determine marching squares index
    i = 0;
    if (grid(x-1, y-1)) i += 1;
    if (grid(x,   y-1)) i += 2;
    if (grid(x-1, y  )) i += 4;
    if (grid(x,   y  )) i += 8;

    // determine next direction
    if (i === 6) {
      dx = pdy === -1 ? -1 : 1;
      dy = 0;
    } else if (i === 9) {
      dx = 0;
      dy = pdx === 1 ? -1 : 1;
    } else {
      dx = d3_geom_contourDx[i];
      dy = d3_geom_contourDy[i];
    }

    // update contour polygon
    if (dx != pdx &amp;&amp; dy != pdy) {
      c.push([x, y]);
      pdx = dx;
      pdy = dy;
    }

    x += dx;
    y += dy;
  } while (s[0] != x || s[1] != y);

  return c;
};

// lookup tables for marching directions
var d3_geom_contourDx = [1, 0, 1, 1,-1, 0,-1, 1,0, 0,0,0,-1, 0,-1,NaN],
    d3_geom_contourDy = [0,-1, 0, 0, 0,-1, 0, 0,1,-1,1,1, 0,-1, 0,NaN];

function d3_geom_contourStart(grid) {
  var x = 0,
      y = 0;

  // search for a starting point; begin at origin
  // and proceed along outward-expanding diagonals
  while (true) {
    if (grid(x,y)) {
      return [x,y];
    }
    if (x === 0) {
      x = y + 1;
      y = 0;
    } else {
      x = x - 1;
      y = y + 1;
    }
  }
}
/**
 * Computes the 2D convex hull of a set of points using Graham's scanning
 * algorithm. The algorithm has been implemented as described in Cormen,
 * Leiserson, and Rivest's Introduction to Algorithms. The running time of
 * this algorithm is O(n log n), where n is the number of input points.
 *
 * @param vertices [[x1, y1], [x2, y2], …]
 * @returns polygon [[x1, y1], [x2, y2], …]
 */
d3.geom.hull = function(vertices) {
  if (vertices.length = (x2*x2 + y2*y2)) {
        points[i].index = -1;
      } else {
        points[u].index = -1;
        a = points[i].angle;
        u = i;
        v = j;
      }
    } else {
      a = points[i].angle;
      u = i;
      v = j;
    }
  }

  // initialize the stack
  stack.push(h);
  for (i=0, j=0; i 0;
}
// Note: requires coordinates to be counterclockwise and convex!
d3.geom.polygon = function(coordinates) {

  coordinates.area = function() {
    var i = 0,
        n = coordinates.length,
        a = coordinates[n - 1][0] * coordinates[0][1],
        b = coordinates[n - 1][1] * coordinates[0][0];
    while (++i = 0) {
      s1 = e.ep.r;
      s2 = e.ep.l;
    } else {
      s1 = e.ep.l;
      s2 = e.ep.r;
    }
    if (e.a === 1) {
      y1 = s1 ? s1.y : -1e6;
      x1 = e.c - e.b * y1;
      y2 = s2 ? s2.y : 1e6;
      x2 = e.c - e.b * y2;
    } else {
      x1 = s1 ? s1.x : -1e6;
      y1 = e.c - e.a * x1;
      x2 = s2 ? s2.x : 1e6;
      y2 = e.c - e.a * x2;
    }
    var v1 = [x1, y1],
        v2 = [x2, y2];
    polygons[e.region.l.index].push(v1, v2);
    polygons[e.region.r.index].push(v1, v2);
  });

  // Reconnect the polygon segments into counterclockwise loops.
  return polygons.map(function(polygon, i) {
    var cx = vertices[i][0],
        cy = vertices[i][1];
    polygon.forEach(function(v) {
      v.angle = Math.atan2(v[0] - cx, v[1] - cy);
    });
    return polygon.sort(function(a, b) {
      return a.angle - b.angle;
    }).filter(function(d, i) {
      return !i || (d.angle - polygon[i - 1].angle &gt; 1e-10);
    });
  });
};

var d3_voronoi_opposite = {"l": "r", "r": "l"};

function d3_voronoi_tessellate(vertices, callback) {

  var Sites = {
    list: vertices
      .map(function(v, i) {
        return {
          index: i,
          x: v[0],
          y: v[1]
        };
      })
      .sort(function(a, b) {
        return a.y  b.y ? 1
          : a.x  b.x ? 1
          : 0;
      }),
    bottomSite: null
  };

  var EdgeList = {
    list: [],
    leftEnd: null,
    rightEnd: null,

    init: function() {
      EdgeList.leftEnd = EdgeList.createHalfEdge(null, "l");
      EdgeList.rightEnd = EdgeList.createHalfEdge(null, "l");
      EdgeList.leftEnd.r = EdgeList.rightEnd;
      EdgeList.rightEnd.l = EdgeList.leftEnd;
      EdgeList.list.unshift(EdgeList.leftEnd, EdgeList.rightEnd);
    },

    createHalfEdge: function(edge, side) {
      return {
        edge: edge,
        side: side,
        vertex: null,
        "l": null,
        "r": null
      };
    },

    insert: function(lb, he) {
      he.l = lb;
      he.r = lb.r;
      lb.r.l = he;
      lb.r = he;
    },

    leftBound: function(p) {
      var he = EdgeList.leftEnd;
      do {
        he = he.r;
      } while (he != EdgeList.rightEnd &amp;&amp; Geom.rightOf(he, p));
      he = he.l;
      return he;
    },

    del: function(he) {
      he.l.r = he.r;
      he.r.l = he.l;
      he.edge = null;
    },

    right: function(he) {
      return he.r;
    },

    left: function(he) {
      return he.l;
    },

    leftRegion: function(he) {
      return he.edge == null
          ? Sites.bottomSite
          : he.edge.region[he.side];
    },

    rightRegion: function(he) {
      return he.edge == null
          ? Sites.bottomSite
          : he.edge.region[d3_voronoi_opposite[he.side]];
    }
  };

  var Geom = {

    bisect: function(s1, s2) {
      var newEdge = {
        region: {"l": s1, "r": s2},
        ep: {"l": null, "r": null}
      };

      var dx = s2.x - s1.x,
          dy = s2.y - s1.y,
          adx = dx &gt; 0 ? dx : -dx,
          ady = dy &gt; 0 ? dy : -dy;

      newEdge.c = s1.x * dx + s1.y * dy
          + (dx * dx + dy * dy) * .5;

      if (adx &gt; ady) {
        newEdge.a = 1;
        newEdge.b = dy / dx;
        newEdge.c /= dx;
      } else {
        newEdge.b = 1;
        newEdge.a = dx / dy;
        newEdge.c /= dy;
      }

      return newEdge;
    },

    intersect: function(el1, el2) {
      var e1 = el1.edge,
          e2 = el2.edge;
      if (!e1 || !e2 || (e1.region.r == e2.region.r)) {
        return null;
      }
      var d = (e1.a * e2.b) - (e1.b * e2.a);
      if (Math.abs(d) = e.region.r.x);
      if ((rightOfSite &amp;&amp; (el.side === "l")) ||
        (!rightOfSite &amp;&amp; (el.side === "r"))) {
        return null;
      }
      return {
        x: xint,
        y: yint
      };
    },

    rightOf: function(he, p) {
      var e = he.edge,
          topsite = e.region.r,
          rightOfSite = (p.x &gt; topsite.x);

      if (rightOfSite &amp;&amp; (he.side === "l")) {
        return 1;
      }
      if (!rightOfSite &amp;&amp; (he.side === "r")) {
        return 0;
      }
      if (e.a === 1) {
        var dyp = p.y - topsite.y,
            dxp = p.x - topsite.x,
            fast = 0,
            above = 0;

        if ((!rightOfSite &amp;&amp; (e.b = 0))) {
          above = fast = (dyp &gt;= e.b * dxp);
        } else {
          above = ((p.x + p.y * e.b) &gt; e.c);
          if (e.b  (t2 * t2 + t3 * t3);
      }
      return he.side === "l" ? above : !above;
    },

    endPoint: function(edge, side, site) {
      edge.ep[side] = site;
      if (!edge.ep[d3_voronoi_opposite[side]]) return;
      callback(edge);
    },

    distance: function(s, t) {
      var dx = s.x - t.x,
          dy = s.y - t.y;
      return Math.sqrt(dx * dx + dy * dy);
    }
  };

  var EventQueue = {
    list: [],

    insert: function(he, site, offset) {
      he.vertex = site;
      he.ystar = site.y + offset;
      for (var i=0, list=EventQueue.list, l=list.length; i next.ystar ||
          (he.ystar == next.ystar &amp;&amp;
          site.x &gt; next.vertex.x)) {
          continue;
        } else {
          break;
        }
      }
      list.splice(i, 0, he);
    },

    del: function(he) {
      for (var i=0, ls=EventQueue.list, l=ls.length; i top.y) {
        temp = bot;
        bot = top;
        top = temp;
        pm = "r";
      }
      e = Geom.bisect(bot, top);
      bisector = EdgeList.createHalfEdge(e, pm);
      EdgeList.insert(llbnd, bisector);
      Geom.endPoint(e, d3_voronoi_opposite[pm], v);
      p = Geom.intersect(llbnd, bisector);
      if (p) {
        EventQueue.del(llbnd);
        EventQueue.insert(llbnd, p, Geom.distance(p, bot));
      }
      p = Geom.intersect(bisector, rrbnd);
      if (p) {
        EventQueue.insert(bisector, p, Geom.distance(p, bot));
      }
    } else {
      break;
    }
  }//end while

  for (lbnd = EdgeList.right(EdgeList.leftEnd);
      lbnd != EdgeList.rightEnd;
      lbnd = EdgeList.right(lbnd)) {
    callback(lbnd.edge);
  }
}
/**
* @param vertices [[x1, y1], [x2, y2], …]
* @returns triangles [[[x1, y1], [x2, y2], [x3, y3]], …]
 */
d3.geom.delaunay = function(vertices) {
  var edges = vertices.map(function() { return []; }),
      triangles = [];

  // Use the Voronoi tessellation to determine Delaunay edges.
  d3_voronoi_tessellate(vertices, function(e) {
    edges[e.region.l.index].push(vertices[e.region.r.index]);
  });

  // Reconnect the edges into counterclockwise triangles.
  edges.forEach(function(edge, i) {
    var v = vertices[i],
        cx = v[0],
        cy = v[1];
    edge.forEach(function(v) {
      v.angle = Math.atan2(v[0] - cx, v[1] - cy);
    });
    edge.sort(function(a, b) {
      return a.angle - b.angle;
    });
    for (var j = 0, m = edge.length - 1; j  x2) x2 = p.x;
        if (p.y &gt; y2) y2 = p.y;
      }

      // Squarify the bounds.
      var dx = x2 - x1,
          dy = y2 - y1;
      if (dx &gt; dy) y2 = y1 + dx;
      else x2 = x1 + dy;
    }
  }

  // Recursively inserts the specified point p at the node n or one of its
  // descendants. The bounds are defined by [x1, x2] and [y1, y2].
  function insert(n, p, x1, y1, x2, y2) {
    if (isNaN(p.x) || isNaN(p.y)) return; // ignore invalid points
    if (n.leaf) {
      var v = n.point;
      if (v) {
        // If the point at this leaf node is at the same position as the new
        // point we are adding, we leave the point associated with the
        // internal node while adding the new point to a child node. This
        // avoids infinite recursion.
        if ((Math.abs(v.x - p.x) + Math.abs(v.y - p.y)) = sx,
        bottom = p.y &gt;= sy,
        i = (bottom  1
      ? Date.UTC.apply(this, arguments)
      : arguments[0]);
}

d3_time_utc.prototype = {
  getDate: function() { return this._.getUTCDate(); },
  getDay: function() { return this._.getUTCDay(); },
  getFullYear: function() { return this._.getUTCFullYear(); },
  getHours: function() { return this._.getUTCHours(); },
  getMilliseconds: function() { return this._.getUTCMilliseconds(); },
  getMinutes: function() { return this._.getUTCMinutes(); },
  getMonth: function() { return this._.getUTCMonth(); },
  getSeconds: function() { return this._.getUTCSeconds(); },
  getTime: function() { return this._.getTime(); },
  getTimezoneOffset: function() { return 0; },
  valueOf: function() { return this._.valueOf(); },
  setDate: function() { d3_time_prototype.setUTCDate.apply(this._, arguments); },
  setDay: function() { d3_time_prototype.setUTCDay.apply(this._, arguments); },
  setFullYear: function() { d3_time_prototype.setUTCFullYear.apply(this._, arguments); },
  setHours: function() { d3_time_prototype.setUTCHours.apply(this._, arguments); },
  setMilliseconds: function() { d3_time_prototype.setUTCMilliseconds.apply(this._, arguments); },
  setMinutes: function() { d3_time_prototype.setUTCMinutes.apply(this._, arguments); },
  setMonth: function() { d3_time_prototype.setUTCMonth.apply(this._, arguments); },
  setSeconds: function() { d3_time_prototype.setUTCSeconds.apply(this._, arguments); },
  setTime: function() { d3_time_prototype.setTime.apply(this._, arguments); }
};

var d3_time_prototype = Date.prototype;
d3.time.format = function(template) {
  var n = template.length;

  function format(date) {
    var string = [],
        i = -1,
        j = 0,
        c,
        f;
    while (++i = m) return -1;
    c = template.charCodeAt(i++);
    if (c == 37) {
      p = d3_time_parsers[template.charAt(i++)];
      if (!p || ((j = p(date, string, j)) = 12 ? "PM" : "AM"; },
  S: function(d) { return d3_time_zfill2(d.getSeconds()); },
  U: function(d) { return d3_time_zfill2(d3.time.sundayOfYear(d)); },
  w: function(d) { return d.getDay(); },
  W: function(d) { return d3_time_zfill2(d3.time.mondayOfYear(d)); },
  x: d3.time.format("%m/%d/%y"),
  X: d3.time.format("%H:%M:%S"),
  y: function(d) { return d3_time_zfill2(d.getFullYear() % 100); },
  Y: function(d) { return d3_time_zfill4(d.getFullYear() % 10000); },
  Z: d3_time_zone,
  "%": function(d) { return "%"; }
};

var d3_time_parsers = {
  a: d3_time_parseWeekdayAbbrev,
  A: d3_time_parseWeekday,
  b: d3_time_parseMonthAbbrev,
  B: d3_time_parseMonth,
  c: d3_time_parseLocaleFull,
  d: d3_time_parseDay,
  e: d3_time_parseDay,
  H: d3_time_parseHour24,
  I: d3_time_parseHour24,
  // j: function(d, s, i) { /*TODO day of year [001,366] */ return i; },
  L: d3_time_parseMilliseconds,
  m: d3_time_parseMonthNumber,
  M: d3_time_parseMinutes,
  p: d3_time_parseAmPm,
  S: d3_time_parseSeconds,
  // U: function(d, s, i) { /*TODO week number (sunday) [00,53] */ return i; },
  // w: function(d, s, i) { /*TODO weekday [0,6] */ return i; },
  // W: function(d, s, i) { /*TODO week number (monday) [00,53] */ return i; },
  x: d3_time_parseLocaleDate,
  X: d3_time_parseLocaleTime,
  y: d3_time_parseYear,
  Y: d3_time_parseFullYear
  // ,
  // Z: function(d, s, i) { /*TODO time zone */ return i; },
  // "%": function(d, s, i) { /*TODO literal % */ return i; }
};

// Note: weekday is validated, but does not set the date.
function d3_time_parseWeekdayAbbrev(date, string, i) {
  return d3_time_weekdayAbbrevRe.test(string.substring(i, i += 3)) ? i : -1;
}

// Note: weekday is validated, but does not set the date.
function d3_time_parseWeekday(date, string, i) {
  d3_time_weekdayRe.lastIndex = 0;
  var n = d3_time_weekdayRe.exec(string.substring(i, i + 10));
  return n ? i += n[0].length : -1;
}

var d3_time_weekdayAbbrevRe = /^(?:sun|mon|tue|wed|thu|fri|sat)/i,
    d3_time_weekdayRe = /^(?:Sunday|Monday|Tuesday|Wednesday|Thursday|Friday|Saturday)/i,
    d3_time_weekdays = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];

function d3_time_parseMonthAbbrev(date, string, i) {
  var n = d3_time_monthAbbrevLookup.get(string.substring(i, i += 3).toLowerCase());
  return n == null ? -1 : (date.m = n, i);
}

var d3_time_monthAbbrevLookup = d3.map({
  jan: 0,
  feb: 1,
  mar: 2,
  apr: 3,
  may: 4,
  jun: 5,
  jul: 6,
  aug: 7,
  sep: 8,
  oct: 9,
  nov: 10,
  dec: 11
});

function d3_time_parseMonth(date, string, i) {
  d3_time_monthRe.lastIndex = 0;
  var n = d3_time_monthRe.exec(string.substring(i, i + 12));
  return n ? (date.m = d3_time_monthLookup.get(n[0].toLowerCase()), i += n[0].length) : -1;
}

var d3_time_monthRe = /^(?:January|February|March|April|May|June|July|August|September|October|November|December)/ig;

var d3_time_monthLookup = d3.map({
  january: 0,
  february: 1,
  march: 2,
  april: 3,
  may: 4,
  june: 5,
  july: 6,
  august: 7,
  september: 8,
  october: 9,
  november: 10,
  december: 11
});

var d3_time_months = [
  "January",
  "February",
  "March",
  "April",
  "May",
  "June",
  "July",
  "August",
  "September",
  "October",
  "November",
  "December"
];

function d3_time_parseLocaleFull(date, string, i) {
  return d3_time_parse(date, d3_time_formats.c.toString(), string, i);
}

function d3_time_parseLocaleDate(date, string, i) {
  return d3_time_parse(date, d3_time_formats.x.toString(), string, i);
}

function d3_time_parseLocaleTime(date, string, i) {
  return d3_time_parse(date, d3_time_formats.X.toString(), string, i);
}

function d3_time_parseFullYear(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 4));
  return n ? (date.y = +n[0], i += n[0].length) : -1;
}

function d3_time_parseYear(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 2));
  return n ? (date.y = d3_time_century() + +n[0], i += n[0].length) : -1;
}

function d3_time_century() {
  return ~~(new Date().getFullYear() / 1000) * 1000;
}

function d3_time_parseMonthNumber(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 2));
  return n ? (date.m = n[0] - 1, i += n[0].length) : -1;
}

function d3_time_parseDay(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 2));
  return n ? (date.d = +n[0], i += n[0].length) : -1;
}

// Note: we don't validate that the hour is in the range [0,23] or [1,12].
function d3_time_parseHour24(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 2));
  return n ? (date.H = +n[0], i += n[0].length) : -1;
}

function d3_time_parseMinutes(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 2));
  return n ? (date.M = +n[0], i += n[0].length) : -1;
}

function d3_time_parseSeconds(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 2));
  return n ? (date.S = +n[0], i += n[0].length) : -1;
}

function d3_time_parseMilliseconds(date, string, i) {
  d3_time_numberRe.lastIndex = 0;
  var n = d3_time_numberRe.exec(string.substring(i, i + 3));
  return n ? (date.L = +n[0], i += n[0].length) : -1;
}

// Note: we don't look at the next directive.
var d3_time_numberRe = /\s*\d+/;

function d3_time_parseAmPm(date, string, i) {
  var n = d3_time_amPmLookup.get(string.substring(i, i += 2).toLowerCase());
  return n == null ? -1 : (date.p = n, i);
}

var d3_time_amPmLookup = d3.map({
  am: 0,
  pm: 1
});

// TODO table of time zone offset names?
function d3_time_zone(d) {
  var z = d.getTimezoneOffset(),
      zs = z &gt; 0 ? "-" : "+",
      zh = ~~(Math.abs(z) / 60),
      zm = Math.abs(z) % 60;
  return zs + d3_time_zfill2(zh) + d3_time_zfill2(zm);
}
d3.time.format.utc = function(template) {
  var local = d3.time.format(template);

  function format(date) {
    try {
      d3_time = d3_time_utc;
      var utc = new d3_time();
      utc._ = date;
      return local(utc);
    } finally {
      d3_time = Date;
    }
  }

  format.parse = function(string) {
    try {
      d3_time = d3_time_utc;
      var date = local.parse(string);
      return date &amp;&amp; date._;
    } finally {
      d3_time = Date;
    }
  };

  format.toString = local.toString;

  return format;
};
var d3_time_formatIso = d3.time.format.utc("%Y-%m-%dT%H:%M:%S.%LZ");

d3.time.format.iso = Date.prototype.toISOString ? d3_time_formatIsoNative : d3_time_formatIso;

function d3_time_formatIsoNative(date) {
  return date.toISOString();
}

d3_time_formatIsoNative.parse = function(string) {
  return new Date(string);
};

d3_time_formatIsoNative.toString = d3_time_formatIso.toString;
function d3_time_interval(local, step, number) {

  function round(date) {
    var d0 = local(date), d1 = offset(d0, 1);
    return date - d0  1) {
      while (time </p>