Circles on an Axis in a Static Force Layout - d3 V5

Code sample to answer this stackoverflow question, on making a beeswarm plot in D3 v5 with variable radius.

Render circles along an axis based on the node's value in a tight formation.

This is a force layout rendered statically. Collisions are detected between circles (see Clustered Force Layout I). Custom gravity drives the circle towards their desired placement along the x-axis. A light preference is employed to center circles on the x-axis respective of their value. This creates a less tightly-packed layout, but the data is represented accurately.

forked from ericandrewlewis's block: Circles on an Axis in a Static Force Layout

<!DOCTYPE html>
<meta charset="utf-8">
<style>
svg {
  font: 10px sans-serif;
}
.x.axis .domain {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}
</style>
<body>
<script src="https://d3js.org/d3.v5.min.js"></script>
<script>

var margin = {top: 50, right: 50, bottom: 50, left: 50},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom,
    // padding between nodes
    padding = 2,
    maxRadius = 1000,
    numberOfNodes = 50;

// Create random node data.
var data = d3.range(numberOfNodes).map(function() {
  var value = Math.floor(Math.random() * 50) / 10,
      size = Math.floor( Math.sqrt((value + 1) / numberOfNodes * -Math.log(Math.random())) * maxRadius * 10 ),
      datum = {value: value, size: size};
  return datum;
});

var x = d3.scaleLinear()
  .domain( [0, 5] )
  .range( [margin.left, width + margin.right]);

// Map the basic node data to d3-friendly format.
var nodes = data.map(function(node, index) {
  return {
    radius: node.size / 100,
    color: '#ff7f0e',
    x: x(node.value),
    y: height / 2 + Math.random()
  };
});

var force = d3.forceSimulation(nodes)
  .force('charge', d3.forceManyBody())
  .force('center', d3.forceCenter(width / 2, height / 2))
  .force('forceX', d3.forceX(d => d.x))
  .force('forceY', d3.forceY(d => d.y))
  .force('collide', d3.forceCollide(d => d.radius))
  .on("tick", tick)
  .stop();

var xAxis = d3.axisBottom(x);

var svg = d3.select("body").append("svg")
  .attr("width", width + margin.left + margin.right)
  .attr("height", height + margin.top + margin.bottom);

var loading = svg.append("text")
  .attr("x", ( width + margin.left + margin.right ) / 2)
  .attr("y", ( height + margin.top + margin.bottom ) / 2)
  .attr("dy", ".35em")
  .style("text-anchor", "middle")
  .text("Simulating. One moment please…");

/**
 * On a tick, apply custom gravity, collision detection, and node placement.
 */
function tick() {

for ( i = 0; i < nodes.length; i++ ) {
    var node = nodes[i];
    node.cx = node.x;
    node.cy = node.y;
  }
}

/**
 * Run the force layout to compute where each node should be placed,
 * then replace the loading text with the graph.
 */
function renderGraph() {
  // Run the layout a fixed number of times.
  // The ideal number of times scales with graph complexity.
  // Of course, don't run too long—you'll hang the page!
  const NUM_ITERATIONS = 100;
  force.tick(NUM_ITERATIONS);
  force.stop();

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + ( margin.top + ( height * 3/4 ) ) + ")")
    .call(xAxis);

var circle = svg.selectAll("circle")
    .data(nodes)
  .enter().append("circle")
    .style("fill", function(d) { return d.color; })
    .attr("cx", function(d) { return d.x} )
    .attr("cy", function(d) { return d.y} )
    .attr("r", function(d) { return d.radius } );

loading.remove();
}
// Use a timeout to allow the rest of the page to load first.
setTimeout(renderGraph, 10);

</script>

https://d3js.org/d3.v5.min.js