Radial cluster tree

D3’s cluster layout produces node-link diagrams with leaf nodes at equal depth. These are less compact than tidy trees, but are useful for dendrograms, hierarchical clustering and phylogenetic trees. See also the Cartesian variant.

// Specify the chart's dimensions.
const width = 960;
const height = width;
const cx = width * 0.5; // adjust as needed to fit
const cy = height * 0.54; // adjust as needed to fit
const radius = Math.min(width, height) / 2 - 80;

// Create a radial cluster layout. The layout’s first dimension (x)
// is the angle, while the second (y) is the radius.
const tree = d3.cluster()
    .size([2 * Math.PI, radius])
    .separation((a, b) => (a.parent == b.parent ? 1 : 2) / a.depth);

// Sort the tree and apply the layout.
const root = tree(d3.hierarchy(data)
    .sort((a, b) => d3.ascending(a.data.name, b.data.name)));

// Creates the SVG container.
const svg = d3.create("svg")
    .attr("width", width)
    .attr("height", height)
    .attr("viewBox", [-cx, -cy, width, height])
    .attr("style", "width: 100%; height: auto; font: 10px sans-serif;");

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

// Append nodes.
svg.append("g")
  .selectAll()
  .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);

// Append labels.
svg.append("g")
    .attr("stroke-linejoin", "round")
    .attr("stroke-width", 3)
  .selectAll()
  .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")
    .attr("paint-order", "stroke")
    .attr("stroke", "white")
    .attr("fill", "currentColor")
    .text((d) => d.data.name);

display(svg.node());

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