Force Directed Layout Quality Convergence

Graph readability metrics can be used to check the convergence rate of graph layout algorithms. This example uses Greadability.js to calculate four graph layout readability metrics at each iteration of the D3's force-directed graph layout algorithm:

Edge crossings measures the fraction of edges that cross (intersect) out of an approximate maximum number that can cross.
Edge crossing angle measures the mean deviation of edge crossing angles from the ideal edge crossing angle (70 degrees).
Angular resolution (minimum) measures the mean deviation of adjacent incident edge angles from the ideal minimum angles (360 degrees divided by the degree of that node).
Angular resoluction (deviation) measures the average deviation of angles between incident edges on each vertex.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

html, body {
  width: 960px;
  height: 600px;
  display: flex;
  align-items: center;
  justify-content: center;
}

svg {
  overflow: visible;
}

.line-g path {
  stroke: #d30000;
}

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
  stroke-width: 2px;
}

.nodes circle {
  fill: #d30000;
  stroke: #fff;
  stroke-width: 1px;
}

</style>
<svg class="graph"></svg>
<svg class="convergence"></svg>
<script src="greadability.js"></script>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var width = 600;
var height = 600;

var convWidth = 360;
var convHeight = 300;
var margin = {left: 40, right: 10, top: 30, bottom: 20};

var metrics = [
  {name: 'Edge crossings', varName: 'crossing', data: []},
  {name: 'Crossing angle', varName: 'crossingAngle', data: []},
  {name: 'Angular resolution (min)', varName: 'angularResolutionMin', data: []},
  {name: 'Angular resolution (dev)', varName: 'angularResolutionDev', data: []}
];

var drag = d3.drag()
  .on('start', dragStart)
  .on('drag', dragging)
  .on('end', dragEnd);

var svg = d3.select('svg.graph')
  .attr('width', width)
  .attr('height', height);

var convSvg = d3.select('svg.convergence')
  .attr('width', convWidth)
  .attr('height', convHeight)
  .append('g')
  .attr('transform', 'translate(' + margin.left + ',' + margin.top + ')');

var x = d3.scaleLinear()
  .domain([0, 300])
  .range([0, (convWidth = convWidth - margin.left - margin.right)]);

var y = d3.scaleLinear()
  .domain([0, 1])
  .range([(convHeight = convHeight - margin.top - margin.bottom), 0]);

var line = d3.line()
    .x(function (d) { return x(d[0]); })
    .y(function (d) { return y(d[1]); });

var forceSim = d3.forceSimulation()
  .force('link', d3.forceLink())
  .force('charge', d3.forceManyBody())
  .force('center', d3.forceCenter(width/2, height/2));

d3.json('miserables.json', function (error, graph) {
  if (error) throw error;

var link = svg.append('g')
    .attr('class', 'links')
    .selectAll('line')
    .data(graph.links)
    .enter().append('line');

var node = svg.append('g')
    .attr('class', 'nodes')
    .selectAll('circle')
    .data(graph.nodes)
    .enter().append('circle')
    .attr('r', 4)
    .call(drag);

node.append('title').text(function (d) { return d.name; });

forceSim.nodes(graph.nodes)
    .on('tick', tick)
    .stop();

forceSim.force('link')
    .links(graph.links);

var graphReadability = greadability.greadability(graph.nodes, graph.links);

metrics.forEach(function (m) {
      var iterNum = 0;
      m.data.push([iterNum, graphReadability[m.varName]]);
    });

forceSim.restart();

node
      .attr('cx', function (d) { return d.x; })
      .attr('cy', function (d) { return d.y; });

var graphReadability = greadability.greadability(graph.nodes, graph.links);

metrics.forEach(function (m) {
      var iterNum = m.data[m.data.length - 1][0] + 1;
      m.data.push([iterNum, graphReadability[m.varName]]);

if (m.data.length > 301) {
        m.data = m.data.slice(metrics.length - 301);
      }
    });

x.domain([metrics[0].data[0][0], metrics[0].data[0][0] + 300]);

convSvg.selectAll('*').remove();

convSvg.append('g')
        .attr('transform', 'translate(0,' + convHeight + ')')
        .call(d3.axisBottom(x).ticks(7))
      .append("text")
        .attr("fill", "#000")
        .attr('transform', 'translate(' + convWidth + ',' + 0 + ')')
        .attr("y", -10)
        .attr("dy", "0.71em")
        .attr("text-anchor", "end")
        .text("Number of iterations");

convSvg.append('g')
        .call(d3.axisLeft(y))
      .append("text")
        .attr("fill", "#000")
        .attr("transform", "rotate(-90)")
        .attr("y", -39)
        .attr("dy", "0.71em")
        .attr("text-anchor", "end")
        .text("Readability score");

var lineG = convSvg.selectAll('g.line-g')
        .data(metrics)
      .enter().append('g')
        .attr('class', function (d) { return 'line-g ' + d.varName; });

lineG.append('path')
        .attr("fill", "none")
        .attr("stroke-linejoin", "round")
        .attr("stroke-linecap", "round")
        .attr("stroke-width", 1.5)
        .attr("d", function (d) { return line(d.data); });

lineG.append("text")
        .datum(function(d) { return {name: d.name, value: d.data[d.data.length - 1]}; })
        .attr("transform", function(d) { return "translate(" + x(d.value[0]) + "," + y(d.value[1]) + ")"; })
        .attr("x", 3)
        .attr('y', -6)
        .attr("dy", "0.35em")
        .attr('text-anchor', 'end')
        .style("font", "10px sans-serif")
        .text(function(d) { return d.name; });
  }
});

function dragStart (d) {
  if (!d3.event.active) forceSim.alphaTarget(0.3).restart();
  d.fx = d.x;
  d.fy = d.y;
}

function dragging (d) {
  d.fx = d3.event.x;
  d.fy = d3.event.y;
}

function dragEnd (d) {
  if (!d3.event.active) forceSim.alphaTarget(0);
  d.fx = null;
  d.fy = null;
}

</script>

https://d3js.org/d3.v4.min.js