Radial tidy tree

D3’s tree layout implements the Reingold–Tilford “tidy” algorithm, improved by Buchheim et al., for constructing hierarchical node-link diagrams. Tidy trees are typically more compact than cluster dendrograms, which place all leaves at the same level. See also the Cartesian variant.

const width = 960;
const radius = width / 2;

const tree = d3.tree()
    .size([2 * Math.PI, radius])
    .separation((a, b) => (a.parent == b.parent ? 1 : 2) / a.depth);

const root = tree(d3.hierarchy(data)
    .sort((a, b) => d3.ascending(a.data.name, b.data.name)));

const svg = d3.create("svg");

svg.append("g")
    .attr("fill", "none")
    .attr("stroke", "#555")
    .attr("stroke-opacity", 0.4)
    .attr("stroke-width", 1.5)
  .selectAll("path")
  .data(root.links())
  .join("path")
    .attr("d", d3.linkRadial()
        .angle((d) => d.x)
        .radius((d) => d.y));

svg.append("g")
  .selectAll("circle")
  .data(root.descendants())
  .join("circle")
    .attr("transform", (d) => `
      rotate(${d.x * 180 / Math.PI - 90})
      translate(${d.y},0)
    `)
    .attr("fill", (d) => d.children ? "#555" : "#999")
    .attr("r", 2.5);

svg.append("g")
    .attr("font-family", "sans-serif")
    .attr("font-size", 10)
    .attr("stroke-linejoin", "round")
    .attr("stroke-width", 3)
  .selectAll("text")
  .data(root.descendants())
  .join("text")
    .attr("transform", (d) => `
      rotate(${d.x * 180 / Math.PI - 90})
      translate(${d.y},0)
      rotate(${d.x >= Math.PI ? 180 : 0})
    `)
    .attr("dy", "0.31em")
    .attr("x", (d) => d.x < Math.PI === !d.children ? 6 : -6)
    .attr("text-anchor", (d) => d.x < Math.PI === !d.children ? "start" : "end")
    .text((d) => d.data.name)
  .clone(true).lower()
    .attr("stroke", "white");

display(svg.node());

svg.call(autoBox);

function autoBox(svg) {
  svg.attr("viewBox", function() {
    const {x, y, width, height} = this.getBBox();
    return [x, y, width, height];
  });
}

const data = FileAttachment("data/flare.json").json().then(display);