D3 Examples - 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>
function getData (data) {
  let nested = d3.nest().key(d => d["Session #"]).entries(data)
  let root = {};
  let parent;
  
  let maxLevel = d3.max(nested, d => d.values.length) - 1;
  
  for (let i = 0; i < maxLevel; i++) {
    let levelActions = getLevelActions(i);
    if (i === 0) {
      root.actionText = levelActions[0].actionText;
      root.children = [];
    } else {
      levelActions.forEach(d => {
        if (parent) {
          let _parent = parent.filter(x => x.actionText === d.parent 
                                      && x.sessions.indexOf(d.sessions[0]) > -1);
          if (_parent.length) {
            if (!_parent[0].children)
              _parent[0].children = [];
            _parent[0].children.push(d)
          }
        } else {
          root.children.push(d)
        }
      })
      parent = levelActions;
    }
  }
  
  function getLevelActions(level) {
    let actions = [];
    for (let j = 0; j < nested.length; j++) {
      let values = nested[j].values;
      if (!values[level]) continue;
​
      let actionText = values[level]["User Action"];
      let action = actions.filter(x => x.actionText == actionText);
      let products = [];
      
      if (level > 0) {
        products = [
          values[level - 1].Prod1,
          values[level - 1].Prod2,
          values[level - 1].Prod3
        ]
      }
      
      if (action.length == 0) {
        actions.push({
          actionText: actionText,
          products: products,
          level: level,
          sessions: [+nested[j].key],
          parent: level == 0 ? null : values[level - 1]["User Action"]
        });
      } else {
        if (level > 0) {
          action = action.filter(x => x.products[0] == values[level - 1].Prod1 && 
                                  x.products[1] == values[level - 1].Prod2 && 
                                  x.products[2] == values[level - 1].Prod3)
          if (action.length == 0) {
            actions.push({
              actionText: actionText,
              products: products,
              level: level,
              sessions: [+nested[j].key],
              parent: values[level - 1]["User Action"]
            });
          } else {
            action[0].sessions.push(+nested[j].key)
          }
        }
      }
    }
    
    return actions;
  }
  return root
  
}
  
d3.csv('data.csv', function (data) {
    var dt = getData(data);
    var tree = data => {
      const root = d3.hierarchy(data);
      root.dx = 20;
      root.dy = 960 / (root.height + 1);
      return d3.tree().nodeSize([root.dx, root.dy])(root);
    }
    
    const root = tree(dt);
​
  let x0 = Infinity;
  let x1 = -x0;
  let maxDepth = 0;
  root.each(d => {
    if (d.x > x1) x1 = d.x;
    if (d.x < x0) x0 = d.x;
    if (d.depth > maxDepth) maxDepth = d.depth
  });
​
  var nodes = root.descendants().reverse();
  var links = root.links();
    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)
        .attr('height', height)
    .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>
​
    