Sankey Diagram with v6

.block

license: mit

README.md

The above example is intended to demonstrate drawing a simple Sankey diagram using v6 of d3.js. It uses the 0.12.3 version of the Sankey plugin.

This is one of the code samples for the update to the book D3 Tips and Tricks to version 6 of d3.js.

d3-sankey.min.js

// https://github.com/d3/d3-sankey v0.12.3 Copyright 2019 Mike Bostock
!function(n,t){"object"==typeof exports&&"undefined"!=typeof module?t(exports,require("d3-array"),require("d3-shape")):"function"==typeof define&&define.amd?define(["exports","d3-array","d3-shape"],t):t((n=n||self).d3=n.d3||{},n.d3,n.d3)}(this,function(n,t,e){"use strict";function o(n){return n.target.depth}function r(n,t){return n.sourceLinks.length?n.depth:t-1}function i(n){return function(){return n}}function s(n,t){return u(n.source,t.source)||n.index-t.index}function f(n,t){return u(n.target,t.target)||n.index-t.index}function u(n,t){return n.y0-t.y0}function c(n){return n.value}function l(n){return n.index}function a(n){return n.nodes}function d(n){return n.links}function h(n,t){const e=n.get(t);if(!e)throw new Error("missing: "+t);return e}function g({nodes:n}){for(const t of n){let n=t.y0,e=n;for(const e of t.sourceLinks)e.y0=n+e.width/2,n+=e.width;for(const n of t.targetLinks)n.y1=e+n.width/2,e+=n.width}}function y(n){return[n.source.x1,n.y0]}function k(n){return[n.target.x0,n.y1]}n.sankey=function(){let n,e,o,y=0,k=0,L=1,p=1,w=24,x=8,m=l,v=r,M=a,b=d,S=6;function z(){const r={nodes:M.apply(null,arguments),links:b.apply(null,arguments)};return function({nodes:n,links:t}){for(const[t,e]of n.entries())e.index=t,e.sourceLinks=[],e.targetLinks=[];const e=new Map(n.map((t,e)=>[m(t,e,n),t]));for(const[n,o]of t.entries()){o.index=n;let{source:t,target:r}=o;"object"!=typeof t&&(t=o.source=h(e,t)),"object"!=typeof r&&(r=o.target=h(e,r)),t.sourceLinks.push(o),r.targetLinks.push(o)}if(null!=o)for(const{sourceLinks:t,targetLinks:e}of n)t.sort(o),e.sort(o)}(r),function({nodes:n}){for(const e of n)e.value=void 0===e.fixedValue?Math.max(t.sum(e.sourceLinks,c),t.sum(e.targetLinks,c)):e.fixedValue}(r),function({nodes:n}){const t=n.length;let e=new Set(n),o=new Set,r=0;for(;e.size;){for(const n of e){n.depth=r;for(const{target:t}of n.sourceLinks)o.add(t)}if(++r>t)throw new Error("circular link");e=o,o=new Set}}(r),function({nodes:n}){const t=n.length;let e=new Set(n),o=new Set,r=0;for(;e.size;){for(const n of e){n.height=r;for(const{source:t}of n.targetLinks)o.add(t)}if(++r>t)throw new Error("circular link");e=o,o=new Set}}(r),function(o){const r=function({nodes:n}){const o=t.max(n,n=>n.depth)+1,r=(L-y-w)/(o-1),i=new Array(o);for(const t of n){const n=Math.max(0,Math.min(o-1,Math.floor(v.call(null,t,o))));t.layer=n,t.x0=y+n*r,t.x1=t.x0+w,i[n]?i[n].push(t):i[n]=[t]}if(e)for(const n of i)n.sort(e);return i}(o);n=Math.min(x,(p-k)/(t.max(r,n=>n.length)-1)),function(e){const o=t.min(e,e=>(p-k-(e.length-1)*n)/t.sum(e,c));for(const t of e){let e=k;for(const r of t){r.y0=e,r.y1=e+r.value*o,e=r.y1+n;for(const n of r.sourceLinks)n.width=n.value*o}e=(p-e+n)/(t.length+1);for(let n=0;n<t.length;++n){const o=t[n];o.y0+=e*(n+1),o.y1+=e*(n+1)}V(t)}}(r);for(let n=0;n<S;++n){const t=Math.pow(.99,n),e=Math.max(1-t,(n+1)/S);E(r,t,e),j(r,t,e)}}(r),g(r),r}function j(n,t,o){for(let r=1,i=n.length;r<i;++r){const i=n[r];for(const n of i){let e=0,o=0;for(const{source:t,value:r}of n.targetLinks){let i=r*(n.layer-t.layer);e+=_(t,n)*i,o+=i}if(!(o>0))continue;let r=(e/o-n.y0)*t;n.y0+=r,n.y1+=r,P(n)}void 0===e&&i.sort(u),q(i,o)}}function E(n,t,o){for(let r=n.length-2;r>=0;--r){const i=n[r];for(const n of i){let e=0,o=0;for(const{target:t,value:r}of n.sourceLinks){let i=r*(t.layer-n.layer);e+=C(n,t)*i,o+=i}if(!(o>0))continue;let r=(e/o-n.y0)*t;n.y0+=r,n.y1+=r,P(n)}void 0===e&&i.sort(u),q(i,o)}}function q(t,e){const o=t.length>>1,r=t[o];H(t,r.y0-n,o-1,e),A(t,r.y1+n,o+1,e),H(t,p,t.length-1,e),A(t,k,0,e)}function A(t,e,o,r){for(;o<t.length;++o){const i=t[o],s=(e-i.y0)*r;s>1e-6&&(i.y0+=s,i.y1+=s),e=i.y1+n}}function H(t,e,o,r){for(;o>=0;--o){const i=t[o],s=(i.y1-e)*r;s>1e-6&&(i.y0-=s,i.y1-=s),e=i.y0-n}}function P({sourceLinks:n,targetLinks:t}){if(void 0===o){for(const{source:{sourceLinks:n}}of t)n.sort(f);for(const{target:{targetLinks:t}}of n)t.sort(s)}}function V(n){if(void 0===o)for(const{sourceLinks:t,targetLinks:e}of n)t.sort(f),e.sort(s)}function _(t,e){let o=t.y0-(t.sourceLinks.length-1)*n/2;for(const{target:r,width:i}of t.sourceLinks){if(r===e)break;o+=i+n}for(const{source:n,width:r}of e.targetLinks){if(n===t)break;o-=r}return o}function C(t,e){let o=e.y0-(e.targetLinks.length-1)*n/2;for(const{source:r,width:i}of e.targetLinks){if(r===t)break;o+=i+n}for(const{target:n,width:r}of t.sourceLinks){if(n===e)break;o-=r}return o}return z.update=function(n){return g(n),n},z.nodeId=function(n){return arguments.length?(m="function"==typeof n?n:i(n),z):m},z.nodeAlign=function(n){return arguments.length?(v="function"==typeof n?n:i(n),z):v},z.nodeSort=function(n){return arguments.length?(e=n,z):e},z.nodeWidth=function(n){return arguments.length?(w=+n,z):w},z.nodePadding=function(t){return arguments.length?(x=n=+t,z):x},z.nodes=function(n){return arguments.length?(M="function"==typeof n?n:i(n),z):M},z.links=function(n){return arguments.length?(b="function"==typeof n?n:i(n),z):b},z.linkSort=function(n){return arguments.length?(o=n,z):o},z.size=function(n){return arguments.length?(y=k=0,L=+n[0],p=+n[1],z):[L-y,p-k]},z.extent=function(n){return arguments.length?(y=+n[0][0],L=+n[1][0],k=+n[0][1],p=+n[1][1],z):[[y,k],[L,p]]},z.iterations=function(n){return arguments.length?(S=+n,z):S},z},n.sankeyCenter=function(n){return n.targetLinks.length?n.depth:n.sourceLinks.length?t.min(n.sourceLinks,o)-1:0},n.sankeyJustify=r,n.sankeyLeft=function(n){return n.depth},n.sankeyLinkHorizontal=function(){return e.linkHorizontal().source(y).target(k)},n.sankeyRight=function(n,t){return t-1-n.height},Object.defineProperty(n,"__esModule",{value:!0})});

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>SANKEY Experiment</title>
<style>

.node rect {
  fill-opacity: .9;
  shape-rendering: crispEdges;
}

.node text {
  pointer-events: none;
  text-shadow: 0 1px 0 #fff;
}

.link {
  fill: none;
  stroke: #000;
  stroke-opacity: .2;
}

.link:hover {
  stroke-opacity: .5;
}

</style>

<body>

<script src="https://d3js.org/d3.v6.min.js"></script>
<script 
    src="https://unpkg.com/d3-sankey@0.12.3/dist/d3-sankey.min.js">
</script>
<script>

// set the dimensions and margins of the graph
var margin = {top: 10, right: 10, bottom: 10, left: 10},
    width = 900 - margin.left - margin.right,
    height = 300 - margin.top - margin.bottom;  

// format variables
var formatNumber = d3.format(",.0f"), // zero decimal places
    format = function(d) { return formatNumber(d); },
    color = d3.scaleOrdinal(d3.schemeCategory10);
  
// append the svg object to the body of the page
var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", 
          "translate(" + margin.left + "," + margin.top + ")");

// Set the sankey diagram properties
var sankey = d3.sankey()
    .nodeWidth(36)
    .nodePadding(40)
    .size([width, height]);

var path = sankey.links();

// load the data
d3.json("sankey.json").then(function(sankeydata) {

  graph = sankey(sankeydata);

// add in the links
  var link = svg.append("g").selectAll(".link")
      .data(graph.links)
    .enter().append("path")
      .attr("class", "link")
      .attr("d", d3.sankeyLinkHorizontal())
      .attr("stroke-width", function(d) { return d.width; });  

// add the link titles
  link.append("title")
        .text(function(d) {
    		    return d.source.name + " → " + 
                d.target.name + "\n" + format(d.value); });

// add in the nodes
  var node = svg.append("g").selectAll(".node")
      .data(graph.nodes)
    .enter().append("g")
      .attr("class", "node");

// add the rectangles for the nodes
  node.append("rect")
      .attr("x", function(d) { return d.x0; })
      .attr("y", function(d) { return d.y0; })
      .attr("height", function(d) { return d.y1 - d.y0; })
      .attr("width", sankey.nodeWidth())
      .style("fill", function(d) { 
		      return d.color = color(d.name.replace(/ .*/, "")); })
      .style("stroke", function(d) { 
		  return d3.rgb(d.color).darker(2); })
    .append("title")
      .text(function(d) { 
		  return d.name + "\n" + format(d.value); });

// add in the title for the nodes
  node.append("text")
      .attr("x", function(d) { return d.x0 - 6; })
      .attr("y", function(d) { return (d.y1 + d.y0) / 2; })
      .attr("dy", "0.35em")
      .attr("text-anchor", "end")
      .text(function(d) { return d.name; })
    .filter(function(d) { return d.x0 < width / 2; })
      .attr("x", function(d) { return d.x1 + 6; })
      .attr("text-anchor", "start");

});
  
</script>

</body>

sankey.js

d3.sankey = function() {
  var sankey = {},
      nodeWidth = 24,
      nodePadding = 8,
      size = [1, 1],
      nodes = [],
      links = [];

  sankey.nodeWidth = function(_) {
    if (!arguments.length) return nodeWidth;
    nodeWidth = +_;
    return sankey;
  };

  sankey.nodePadding = function(_) {
    if (!arguments.length) return nodePadding;
    nodePadding = +_;
    return sankey;
  };

  sankey.nodes = function(_) {
    if (!arguments.length) return nodes;
    nodes = _;
    return sankey;
  };

  sankey.links = function(_) {
    if (!arguments.length) return links;
    links = _;
    return sankey;
  };

  sankey.size = function(_) {
    if (!arguments.length) return size;
    size = _;
    return sankey;
  };

  sankey.layout = function(iterations) {
    computeNodeLinks();
    computeNodeValues();
    computeNodeBreadths();
    computeNodeDepths(iterations);
    computeLinkDepths();
    return sankey;
  };

  sankey.relayout = function() {
    computeLinkDepths();
    return sankey;
  };

  sankey.link = function() {
    var curvature = .5;

    function link(d) {
      var x0 = d.source.x + d.source.dx,
          x1 = d.target.x,
          xi = d3.interpolateNumber(x0, x1),
          x2 = xi(curvature),
          x3 = xi(1 - curvature),
          y0 = d.source.y + d.sy + d.dy / 2,
          y1 = d.target.y + d.ty + d.dy / 2;
      return "M" + x0 + "," + y0
           + "C" + x2 + "," + y0
           + " " + x3 + "," + y1
           + " " + x1 + "," + y1;
    }

    link.curvature = function(_) {
      if (!arguments.length) return curvature;
      curvature = +_;
      return link;
    };

    return link;
  };

  // Populate the sourceLinks and targetLinks for each node.
  // Also, if the source and target are not objects, assume they are indices.
  function computeNodeLinks() {
    nodes.forEach(function(node) {
      node.sourceLinks = [];
      node.targetLinks = [];
    });
    links.forEach(function(link) {
      var source = link.source,
          target = link.target;
      if (typeof source === "number") source = link.source = nodes[link.source];
      if (typeof target === "number") target = link.target = nodes[link.target];
      source.sourceLinks.push(link);
      target.targetLinks.push(link);
    });
  }

  // Compute the value (size) of each node by summing the associated links.
  function computeNodeValues() {
    nodes.forEach(function(node) {
      node.value = Math.max(
        d3.sum(node.sourceLinks, value),
        d3.sum(node.targetLinks, value)
      );
    });
  }

  // Iteratively assign the breadth (x-position) for each node.
  // Nodes are assigned the maximum breadth of incoming neighbors plus one;
  // nodes with no incoming links are assigned breadth zero, while
  // nodes with no outgoing links are assigned the maximum breadth.
  function computeNodeBreadths() {
    var remainingNodes = nodes,
        nextNodes,
        x = 0;

    while (remainingNodes.length) {
      nextNodes = [];
      remainingNodes.forEach(function(node) {
        node.x = x;
        node.dx = nodeWidth;
        node.sourceLinks.forEach(function(link) {
          if (nextNodes.indexOf(link.target) < 0) {
            nextNodes.push(link.target);
          }
        });
      });
      remainingNodes = nextNodes;
      ++x;
    }

    //
    moveSinksRight(x);
    scaleNodeBreadths((size[0] - nodeWidth) / (x - 1));
  }

  function moveSourcesRight() {
    nodes.forEach(function(node) {
      if (!node.targetLinks.length) {
        node.x = d3.min(node.sourceLinks, function(d) { return d.target.x; }) - 1;
      }
    });
  }

  function moveSinksRight(x) {
    nodes.forEach(function(node) {
      if (!node.sourceLinks.length) {
        node.x = x - 1;
      }
    });
  }

  function scaleNodeBreadths(kx) {
    nodes.forEach(function(node) {
      node.x *= kx;
    });
  }

  function computeNodeDepths(iterations) {
    var nodesByBreadth = d3.nest()
        .key(function(d) { return d.x; })
        .sortKeys(d3.ascending)
        .entries(nodes)
        .map(function(d) { return d.values; });

    //
    initializeNodeDepth();
    resolveCollisions();
    for (var alpha = 1; iterations > 0; --iterations) {
      relaxRightToLeft(alpha *= .99);
      resolveCollisions();
      relaxLeftToRight(alpha);
      resolveCollisions();
    }

    function initializeNodeDepth() {
      var ky = d3.min(nodesByBreadth, function(nodes) {
        return (size[1] - (nodes.length - 1) * nodePadding) / d3.sum(nodes, value);
      });

      nodesByBreadth.forEach(function(nodes) {
        nodes.forEach(function(node, i) {
          node.y = i;
          node.dy = node.value * ky;
        });
      });

      links.forEach(function(link) {
        link.dy = link.value * ky;
      });
    }

    function relaxLeftToRight(alpha) {
      nodesByBreadth.forEach(function(nodes, breadth) {
        nodes.forEach(function(node) {
          if (node.targetLinks.length) {
            var y = d3.sum(node.targetLinks, weightedSource) / d3.sum(node.targetLinks, value);
            node.y += (y - center(node)) * alpha;
          }
        });
      });

      function weightedSource(link) {
        return center(link.source) * link.value;
      }
    }

    function relaxRightToLeft(alpha) {
      nodesByBreadth.slice().reverse().forEach(function(nodes) {
        nodes.forEach(function(node) {
          if (node.sourceLinks.length) {
            var y = d3.sum(node.sourceLinks, weightedTarget) / d3.sum(node.sourceLinks, value);
            node.y += (y - center(node)) * alpha;
          }
        });
      });

      function weightedTarget(link) {
        return center(link.target) * link.value;
      }
    }

    function resolveCollisions() {
      nodesByBreadth.forEach(function(nodes) {
        var node,
            dy,
            y0 = 0,
            n = nodes.length,
            i;

        // Push any overlapping nodes down.
        nodes.sort(ascendingDepth);
        for (i = 0; i < n; ++i) {
          node = nodes[i];
          dy = y0 - node.y;
          if (dy > 0) node.y += dy;
          y0 = node.y + node.dy + nodePadding;
        }

        // If the bottommost node goes outside the bounds, push it back up.
        dy = y0 - nodePadding - size[1];
        if (dy > 0) {
          y0 = node.y -= dy;

          // Push any overlapping nodes back up.
          for (i = n - 2; i >= 0; --i) {
            node = nodes[i];
            dy = node.y + node.dy + nodePadding - y0;
            if (dy > 0) node.y -= dy;
            y0 = node.y;
          }
        }
      });
    }

    function ascendingDepth(a, b) {
      return a.y - b.y;
    }
  }

  function computeLinkDepths() {
    nodes.forEach(function(node) {
      node.sourceLinks.sort(ascendingTargetDepth);
      node.targetLinks.sort(ascendingSourceDepth);
    });
    nodes.forEach(function(node) {
      var sy = 0, ty = 0;
      node.sourceLinks.forEach(function(link) {
        link.sy = sy;
        sy += link.dy;
      });
      node.targetLinks.forEach(function(link) {
        link.ty = ty;
        ty += link.dy;
      });
    });

    function ascendingSourceDepth(a, b) {
      return a.source.y - b.source.y;
    }

    function ascendingTargetDepth(a, b) {
      return a.target.y - b.target.y;
    }
  }

  function center(node) {
    return node.y + node.dy / 2;
  }

  function value(link) {
    return link.value;
  }

  return sankey;
};

sankey.json

{
"nodes":[
{"node":0,"name":"node0"},
{"node":1,"name":"node1"},
{"node":2,"name":"node2"},
{"node":3,"name":"node3"},
{"node":4,"name":"node4"}
],
"links":[
{"source":0,"target":2,"value":2},
{"source":1,"target":2,"value":2},
{"source":1,"target":3,"value":2},
{"source":0,"target":4,"value":2},
{"source":2,"target":3,"value":2},
{"source":2,"target":4,"value":2},
{"source":3,"target":4,"value":4}
]}