Chord Diagram Code

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<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  font: 10px sans-serif;
}

.group-tick line {
  stroke: #000;
}

.ribbons {
  fill-opacity: 0.67;
}

</style>
<svg width="550" height="550"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var matrix = [
  [11975,  5871, 8916, 2868],
  [ 1951, 10048, 2060, 6171],
  [ 8010, 16145, 8090, 8045],
  [ 1013,   990,  940, 6907]
];

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height"),
    outerRadius = Math.min(width, height) * 0.5 - 40,
    innerRadius = outerRadius - 30;

var formatValue = d3.formatPrefix(",.0", 1e3);

var chord = d3.chord()
    .padAngle(0.05)
    .sortSubgroups(d3.descending);

var arc = d3.arc()
    .innerRadius(innerRadius)
    .outerRadius(outerRadius);

var ribbon = d3.ribbon()
    .radius(innerRadius);

var color = d3.scaleOrdinal()
    .domain(d3.range(4))
    .range(["#000000", "#FFDD89", "#957244", "#F26223"]);

var g = svg.append("g")
    .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")")
    .datum(chord(matrix));

var group = g.append("g")
    .attr("class", "groups")
  .selectAll("g")
  .data(function(chords) { return chords.groups; })
  .enter().append("g");

group.append("path")
    .style("fill", function(d) { return color(d.index); })
    .style("stroke", function(d) { return d3.rgb(color(d.index)).darker(); })
    .attr("d", arc);

var groupTick = group.selectAll(".group-tick")
  .data(function(d) { return groupTicks(d, 1e3); })
  .enter().append("g")
    .attr("class", "group-tick")
    .attr("transform", function(d) { return "rotate(" + (d.angle * 180 / Math.PI - 90) + ") translate(" + outerRadius + ",0)"; });

groupTick.append("line")
    .attr("x2", 6);

groupTick
  .filter(function(d) { return d.value % 5e3 === 0; })
  .append("text")
    .attr("x", 8)
    .attr("dy", ".35em")
    .attr("transform", function(d) { return d.angle > Math.PI ? "rotate(180) translate(-16)" : null; })
    .style("text-anchor", function(d) { return d.angle > Math.PI ? "end" : null; })
    .text(function(d) { return formatValue(d.value); });

g.append("g")
    .attr("class", "ribbons")
  .selectAll("path")
  .data(function(chords) { return chords; })
  .enter().append("path")
    .attr("d", ribbon)
    .style("fill", function(d) { return color(d.target.index); })
    .style("stroke", function(d) { return d3.rgb(color(d.target.index)).darker(); });

// Returns an array of tick angles and values for a given group and step.
function groupTicks(d, step) {
  var k = (d.endAngle - d.startAngle) / d.value;
  return d3.range(0, d.value, step).map(function(value) {
    return {value: value, angle: value * k + d.startAngle};
  });
}
  </script>
</body>

https://d3js.org/d3.v4.min.js