This randomly-generated tree is positioned using a force simulation.
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June 10, 2024 11:28
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Force-Directed Tree
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license: gpl-3.0 | |
height: 960 | |
redirect: https://observablehq.com/@d3/force-directed-tree |
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<!DOCTYPE html> | |
<meta charset="utf-8"> | |
<canvas width="960" height="960"></canvas> | |
<script src="https://d3js.org/d3.v4.min.js"></script> | |
<script> | |
var nodes = d3.range(1000).map(function(i) { | |
return { | |
index: i | |
}; | |
}); | |
var links = d3.range(nodes.length - 1).map(function(i) { | |
return { | |
source: Math.floor(Math.sqrt(i)), | |
target: i + 1 | |
}; | |
}); | |
var simulation = d3.forceSimulation(nodes) | |
.force("charge", d3.forceManyBody()) | |
.force("link", d3.forceLink(links).distance(20).strength(1)) | |
.force("x", d3.forceX()) | |
.force("y", d3.forceY()) | |
.on("tick", ticked); | |
var canvas = document.querySelector("canvas"), | |
context = canvas.getContext("2d"), | |
width = canvas.width, | |
height = canvas.height; | |
d3.select(canvas) | |
.call(d3.drag() | |
.container(canvas) | |
.subject(dragsubject) | |
.on("start", dragstarted) | |
.on("drag", dragged) | |
.on("end", dragended)); | |
function ticked() { | |
context.clearRect(0, 0, width, height); | |
context.save(); | |
context.translate(width / 2, height / 2); | |
context.beginPath(); | |
links.forEach(drawLink); | |
context.strokeStyle = "#aaa"; | |
context.stroke(); | |
context.beginPath(); | |
nodes.forEach(drawNode); | |
context.fill(); | |
context.strokeStyle = "#fff"; | |
context.stroke(); | |
context.restore(); | |
} | |
function dragsubject() { | |
return simulation.find(d3.event.x - width / 2, d3.event.y - height / 2); | |
} | |
function dragstarted() { | |
if (!d3.event.active) simulation.alphaTarget(0.3).restart(); | |
d3.event.subject.fx = d3.event.subject.x; | |
d3.event.subject.fy = d3.event.subject.y; | |
} | |
function dragged() { | |
d3.event.subject.fx = d3.event.x; | |
d3.event.subject.fy = d3.event.y; | |
} | |
function dragended() { | |
if (!d3.event.active) simulation.alphaTarget(0); | |
d3.event.subject.fx = null; | |
d3.event.subject.fy = null; | |
} | |
function drawLink(d) { | |
context.moveTo(d.source.x, d.source.y); | |
context.lineTo(d.target.x, d.target.y); | |
} | |
function drawNode(d) { | |
context.moveTo(d.x + 3, d.y); | |
context.arc(d.x, d.y, 3, 0, 2 * Math.PI); | |
} | |
</script> |
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