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 radial variant.

const width = 960;

const root = d3.hierarchy(data);
root.dx = 10;
root.dy = width / (root.height + 1);

d3.tree().nodeSize([root.dx, root.dy])(root);

let x0 = Infinity;
let x1 = -x0;
root.each((d) => {
  if (d.x > x1) x1 = d.x;
  if (d.x < x0) x0 = d.x;
});

const svg = d3.create("svg")
    .attr("viewBox", [0, 0, width, x1 - x0 + root.dx * 2]);

const g = svg.append("g")
    .attr("font-family", "sans-serif")
    .attr("font-size", 10)
    .attr("transform", `translate(${root.dy / 3},${root.dx - x0})`);

const link = g.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.linkHorizontal()
        .x((d) => d.y)
        .y((d) => d.x));

const node = g.append("g")
    .attr("stroke-linejoin", "round")
    .attr("stroke-width", 3)
  .selectAll("g")
  .data(root.descendants())
  .join("g")
    .attr("transform", (d) => `translate(${d.y},${d.x})`);

node.append("circle")
    .attr("fill", (d) => d.children ? "#555" : "#999")
    .attr("r", 2.5);

node.append("text")
    .attr("dy", "0.31em")
    .attr("x", (d) => d.children ? -6 : 6)
    .attr("text-anchor", (d) => d.children ? "end" : "start")
    .text((d) => d.data.name)
  .clone(true).lower()
    .attr("stroke", "white");

display(svg.node());

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