stats_server/views/statics/vendors/3d/d3.js
function chord(d, i) {
    var s = subgroup(this, source, d, i),
        t = subgroup(this, target, d, i);
    return "M" + s.p0
      + arc(s.r, s.p1) + (equals(s, t)
      ? curve(s.r, s.p1, s.r, s.p0)
      : curve(s.r, s.p1, t.r, t.p0)
      + arc(t.r, t.p1)
      + curve(t.r, t.p1, s.r, s.p0))
      + "Z";
  }
function chord(d, i) {
    var s = subgroup(this, source, d, i),
        t = subgroup(this, target, d, i);
    return "M" + s.p0
      + arc(s.r, s.p1) + (equals(s, t)
      ? curve(s.r, s.p1, s.r, s.p0)
      : curve(s.r, s.p1, t.r, t.p0)
      + arc(t.r, t.p1)
      + curve(t.r, t.p1, s.r, s.p0))
      + "Z";
  }
TODO Allow control point to be customized.