Generating random Dorling cartograms using a force simulation.
Could probably improve performance a little by running the next simulation during the animation instead of waiting until it's done.
See also: Pseudo-Dorling cartogram
Last active
June 3, 2017 00:43
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Dorling cartogram transitions
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| path { | |
| stroke: #000; | |
| stroke-width: 1px; | |
| } | |
| </style> | |
| <body> | |
| <svg width="960", height="600"></svg> | |
| <script src="https://d3js.org/d3.v4.min.js"></script> | |
| <script src="https://cdnjs.cloudflare.com/ajax/libs/topojson/3.0.0/topojson.min.js"></script> | |
| <script src="https://d3js.org/d3-scale-chromatic.v1.min.js"></script> | |
| <script> | |
| var svg = d3.select("svg"), | |
| width = +svg.attr("width"), | |
| height = +svg.attr("height"), | |
| radius = d3.scaleSqrt().range([0, 45]).clamp(true), | |
| randomizer = d3.randomNormal(0.5, 0.2), | |
| color = d3.scaleLinear(); | |
| d3.json("us.json", function(err, us) { | |
| var neighbors = topojson.neighbors(us.objects.states.geometries), | |
| nodes = topojson.feature(us, us.objects.states).features; | |
| nodes.forEach(function(node, i) { | |
| var centroid = d3.geoPath().centroid(node); | |
| node.x0 = centroid[0]; | |
| node.y0 = centroid[1]; | |
| cleanUpGeometry(node); | |
| }); | |
| var states = svg.selectAll("path") | |
| .data(nodes) | |
| .enter() | |
| .append("path") | |
| .attr("d", pathString) | |
| .attr("fill", "#ccc"); | |
| simulate(); | |
| function simulate() { | |
| nodes.forEach(function(node) { | |
| node.x = node.x0; | |
| node.y = node.y0; | |
| node.r = radius(randomizer()); | |
| }); | |
| color.domain(d3.extent(nodes, d => d.r)); | |
| var links = d3.merge(neighbors.map(function(neighborSet, i) { | |
| return neighborSet.filter(j => nodes[j]).map(function(j) { | |
| return {source: i, target: j, distance: nodes[i].r + nodes[j].r + 3}; | |
| }); | |
| })); | |
| var simulation = d3.forceSimulation(nodes) | |
| .force("cx", d3.forceX().x(d => width / 2).strength(0.02)) | |
| .force("cy", d3.forceY().y(d => height / 2).strength(0.02)) | |
| .force("link", d3.forceLink(links).distance(d => d.distance)) | |
| .force("x", d3.forceX().x(d => d.x).strength(0.1)) | |
| .force("y", d3.forceY().y(d => d.y).strength(0.1)) | |
| .force("collide", d3.forceCollide().strength(0.8).radius(d => d.r + 3)) | |
| .stop(); | |
| while (simulation.alpha() > 0.1) { | |
| simulation.tick(); | |
| } | |
| nodes.forEach(function(node){ | |
| var circle = pseudocircle(node), | |
| closestPoints = node.rings.slice(1).map(function(ring){ | |
| var i = d3.scan(circle.map(point => distance(point, ring.centroid))); | |
| return ring.map(() => circle[i]); | |
| }), | |
| interpolator = d3.interpolateArray(node.rings, [circle, ...closestPoints]); | |
| node.interpolator = function(t){ | |
| var str = pathString(interpolator(t)); | |
| // Prevent some fill-rule flickering for MultiPolygons | |
| if (t > 0.99) { | |
| return str.split("Z")[0] + "Z"; | |
| } | |
| return str; | |
| }; | |
| }); | |
| states | |
| .sort((a, b) => b.r - a.r) | |
| .transition() | |
| .delay(1000) | |
| .duration(1500) | |
| .attrTween("d", node => node.interpolator) | |
| .attr("fill", d => d3.interpolateSpectral(color(d.r))) | |
| .transition() | |
| .delay(1000) | |
| .attrTween("d", node => t => node.interpolator(1 - t)) | |
| .attr("fill", "#ccc") | |
| .on("end", (d, i) => i || simulate()); | |
| } | |
| }); | |
| function pseudocircle(node) { | |
| return node.rings[0].map(function(point){ | |
| var angle = node.startingAngle - 2 * Math.PI * (point.along / node.perimeter); | |
| return [ | |
| Math.cos(angle) * node.r + node.x, | |
| Math.sin(angle) * node.r + node.y | |
| ]; | |
| }); | |
| } | |
| function cleanUpGeometry(node) { | |
| node.rings = (node.geometry.type === "Polygon" ? [node.geometry.coordinates] : node.geometry.coordinates); | |
| node.rings = node.rings.map(function(polygon){ | |
| polygon[0].area = d3.polygonArea(polygon[0]); | |
| polygon[0].centroid = d3.polygonCentroid(polygon[0]); | |
| return polygon[0]; | |
| }); | |
| node.rings.sort((a, b) => b.area - a.area); | |
| node.perimeter = d3.polygonLength(node.rings[0]); | |
| // Optional step, but makes for more circular circles | |
| bisect(node.rings[0], node.perimeter / 72); | |
| node.rings[0].reduce(function(prev, point){ | |
| point.along = prev ? prev.along + distance(point, prev) : 0; | |
| node.perimeter = point.along; | |
| return point; | |
| }, null); | |
| node.startingAngle = Math.atan2(node.rings[0][0][1] - node.y0, node.rings[0][0][0] - node.x0); | |
| } | |
| function bisect(ring, maxSegmentLength) { | |
| for (var i = 0; i < ring.length; i++) { | |
| var a = ring[i], b = i === ring.length - 1 ? ring[0] : ring[i + 1]; | |
| while (distance(a, b) > maxSegmentLength) { | |
| b = midpoint(a, b); | |
| ring.splice(i + 1, 0, b); | |
| } | |
| } | |
| } | |
| function distance(a, b) { | |
| return Math.sqrt((a[0] - b[0]) * (a[0] - b[0]) + (a[1] - b[1]) * (a[1] - b[1])); | |
| } | |
| function midpoint(a, b) { | |
| return [a[0] + (b[0] - a[0]) * 0.5, a[1] + (b[1] - a[1]) * 0.5]; | |
| } | |
| function pathString(d) { | |
| return (d.rings || d).map(ring => "M" + ring.join("L") + "Z").join(" "); | |
| } | |
| </script> |
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