chart = {
const width = 1080;
const height = width;
const innerRadius = Math.min(width, height) * 0.5 - 90;
const outerRadius = innerRadius + 10;
const names = d3.sort(d3.union(data.map(d => d.source), data.map(d => d.target)));
const index = new Map(names.map((name, i) => [name, i]));
const matrix = Array.from(index, () => new Array(names.length).fill(0));
for (const {source, target, value} of data) matrix[index.get(source)][index.get(target)] += value;
const chord = d3.chordDirected()
.padAngle(10 / innerRadius)
.sortSubgroups(d3.descending)
.sortChords(d3.descending);
const arc = d3.arc()
.innerRadius(innerRadius)
.outerRadius(outerRadius);
const ribbon = d3.ribbonArrow()
.radius(innerRadius - 1)
.padAngle(1 / innerRadius);
const colors = d3.quantize(d3.interpolateRainbow, names.length);
const svg = d3.create("svg")
.attr("width", width)
.attr("height", height)
.attr("viewBox", [-width / 2, -height / 2, width, height])
.attr("style", "width: 100%; height: auto; font: 10px sans-serif;");
const chords = chord(matrix);
const group = svg.append("g")
.selectAll()
.data(chords.groups)
.join("g");
group.append("path")
.attr("fill", d => colors[d.index])
.attr("d", arc);
group.append("text")
.each(d => (d.angle = (d.startAngle + d.endAngle) / 2))
.attr("dy", "0.35em")
.attr("transform", d => `
rotate(${(d.angle * 180 / Math.PI - 90)})
translate(${outerRadius + 5})
${d.angle > Math.PI ? "rotate(180)" : ""}
`)
.attr("text-anchor", d => d.angle > Math.PI ? "end" : null)
.text(d => names[d.index]);
group.append("title")
.text(d => `${names[d.index]}
${d3.sum(chords, c => (c.source.index === d.index) * c.source.value)} outgoing →
${d3.sum(chords, c => (c.target.index === d.index) * c.source.value)} incoming ←`);
svg.append("g")
.attr("fill-opacity", 0.75)
.selectAll()
.data(chords)
.join("path")
.style("mix-blend-mode", "multiply")
.attr("fill", d => colors[d.target.index])
.attr("d", ribbon)
.append("title")
.text(d => `${names[d.source.index]} → ${names[d.target.index]} ${d.source.value}`);
return svg.node();
}