Chord Arc Labels

Example of curved textPaths in arcs, based on this fiddle by Susa Merz.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
  font-family: sans-serif;
  font-size: 40px;
}
</style>
<body>
<script src="https://d3js.org/d3.v3.js"></script>
<script src="https://d3js.org/colorbrewer.v1.min.js"></script>
<script>
var matrix = d3.range(6).map(function(row) {
  return d3.range(6).map(function(col) {
    return Math.pow(Math.random(),1.5);
  });
});

var width = 960,
    height = 500,
    innerRadius = Math.min(width, height) * 0.4,
    outerRadius = innerRadius + 40;

var fill = d3.scale.ordinal()
  .range(colorbrewer.Spectral[6]);

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height)
  .append("g")
    .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");

var chord = d3.layout.chord()
    .padding(0.05)
    .sortSubgroups(d3.descending)
    .matrix(matrix);

svg.selectAll("path")
    .data(chord.groups)
  .enter().append("path")
    .style("fill", function(d) { return fill(d.index); })
    .style("stroke", "black") 
    .style("opacity",0.5)
    .attr("d", d3.svg.arc().innerRadius(innerRadius).outerRadius(outerRadius))
    .attr("class","arc")
    .attr("id",function(d,i){return "group"+i;});

svg.selectAll("text")
    .data(chord.groups)
  .enter().append("text")
    .attr("dx", 4)
    .attr("dy", 35)
  .append("textPath")
    .attr("class", "label")
    .attr("xlink:href", function(d) { return "#group" + d.index; })
    .text(function(d) { return "Arc " + d.index; })
    .style("fill", function(d) { return d3.rgb(fill(d.index)).darker(2); });

svg.append("g")
    .attr("class", "chord")
  .selectAll("path")
    .data(chord.chords)
  .enter().append("path")
    .attr("d", d3.svg.chord().radius(innerRadius))
    .style("fill", function(d) {
      var chordcolor = d3.scale.linear()
        .range([fill(d.target.index), fill(d.source.index)])
        .domain([-1,1])
        .interpolate(d3.interpolateLab);
      var weight = (d.source.value - d.target.value) / (d.source.value + d.target.value);
      return chordcolor(weight);
    })
    .style("stroke","black")
    .style("opacity", 0.2);

d3.select(self.frameElement).style("height", height + "px");
</script>

Modified http://d3js.org/d3.v3.js to a secure url

Modified http://d3js.org/colorbrewer.v1.min.js to a secure url

https://d3js.org/d3.v3.js

https://d3js.org/colorbrewer.v1.min.js