Sankey with circular references

<!DOCTYPE html>
<html>
<head>

<title>Sankey Diagram</title>
<style>

#chart {
  height: 800px;
}

.node rect {
  cursor: move;
  fill-opacity: .9;
  shape-rendering: crispEdges;
}

.node text {
  pointer-events: none;
  text-shadow: 0 1px 0 #fff;
}

.link {
  fill: none;
  stroke: #000;
  stroke-opacity: .2;
}

.cycleLink {
  fill: #600;
  opacity: .2;
  stroke: none;
  stroke-linejoin: "round";
}

.cycleLink:hover {
  opacity: .5;
}

.link:hover {
  stroke-opacity: .5;
}

</style>
</head>
<body>

<h2>Random Chart</h2>
<p>The chart below is made from randomly generated data.
If it looks strange, try refreshing a few times.

</p>
<p>
The hope is to generate cycles in the data.
The cycles are styled as red to call them out for this example.
This rendering contains what I arrived at as the most reasonable
representation of cycles, featuring a smaller 'lane' at the top 
of the chart where cycles travel.
</p>

var margin = {top: 1, right: 1, bottom: 6, left: 1},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var formatNumber = d3.format(",.0f"),
    format = function(d) { return formatNumber(d) + " tuples"; },
    color = d3.scale.category20();

var sankey = d3.sankey()
    .nodeWidth(15)
    .nodePadding(10)
    .size([width, height]);

var svg = d3.select("#chart").append("svg")
  .attr( "preserveAspectRatio", "xMinYMid meet" )
  .attr("width", width + margin.left + margin.right)
  .attr("height", height + margin.top + margin.bottom);

var rootGraphic = svg
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var path = sankey.link();

function createChart( energy ) {
  sankey
      .nodes(energy.nodes)
      .links(energy.links)
      .layout(32);

link.append("title")
      .text(function(d) { return d.source.name + " -> " + d.target.name + "\n" + format(d.value); });

node.append("rect")
      .attr("height", function(d) { return d.dy; })
      .attr("width", sankey.nodeWidth())
      .style("fill", function(d) { return d.color = color(d.name.replace(/ .*/, "")); })
      .style("stroke", function(d) { return d3.rgb(d.color).darker(2); })
    .append("title")
      .text(function(d) { return d.name + "\n" + format(d.value); });

node.append("text")
      .attr("x", -6)
      .attr("y", function(d) { return d.dy / 2; })
      .attr("dy", ".35em")
      .attr("text-anchor", "end")
      .attr("transform", null)
      .text(function(d) { return d.name; })
    .filter(function(d) { return d.x < width / 2; })
      .attr("x", 6 + sankey.nodeWidth())
      .attr("text-anchor", "start");
	  
  function dragmove(d) {
    d3.select(this).attr("transform", "translate(" + d.x + "," + (d.y = Math.max(0, Math.min(height - d.dy, d3.event.y))) + ")");
    sankey.relayout();
    link.attr("d", path);
  }
  
  // I need to learn javascript
  var numCycles = 0;
  for( var i = 0; i< sankey.links().length; i++ ) {
    if( sankey.links()[i].causesCycle ) {
      numCycles++;
    }
  }

var cycleTopMarginSize = (sankey.cycleLaneDistFromFwdPaths() - 
	    ( (sankey.cycleLaneNarrowWidth() + sankey.cycleSmallWidthBuffer() ) * numCycles ) ) 
  var horizontalMarginSize = ( sankey.cycleDistFromNode() + sankey.cycleControlPointDist() );	  
  
  svg = d3.select("#chart").select("svg")
    .attr( "viewBox", 
	  "" + (0 - horizontalMarginSize ) + " "         // left
	  + cycleTopMarginSize + " "                     // top
	  + (960 + horizontalMarginSize * 2 ) + " "     // width
	  + (500 + (-1 * cycleTopMarginSize)) + " " );  // height
};

var energyData = generateRandomData();

createChart( energyData );
</script>
</body>
</html>

Modified http://d3js.org/d3.v2.js to a secure url

https://d3js.org/d3.v2.js