This is not a true Demers cartogram; it lacks links between adjacent features. Instead of trying to preserve connectedness, this pseudo-cartogram tries to preserve locality, putting each square as close as possible to its origin without overlapping.
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July 18, 2016 19:32
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Pseudo-Demers Cartogram
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| license: gpl-3.0 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <title>Demers Cartogram</title> | |
| <style> | |
| rect { | |
| fill: #eee; | |
| stroke: #000; | |
| stroke-width: 1.5px; | |
| } | |
| </style> | |
| <svg width="960" height="500"></svg> | |
| <script src="https://d3js.org/d3.v4.min.js"></script> | |
| <script> | |
| // Ratio of Obese (BMI >= 30) in U.S. Adults, CDC 2008 | |
| var valueById = [ | |
| NaN, 0.187, 0.198, NaN, 0.133, 0.175, 0.151, NaN, 0.100, 0.125, | |
| 0.171, NaN, 0.172, 0.133, NaN, 0.108, 0.142, 0.167, 0.201, 0.175, | |
| 0.159, 0.169, 0.177, 0.141, 0.163, 0.117, 0.182, 0.153, 0.195, 0.189, | |
| 0.134, 0.163, 0.133, 0.151, 0.145, 0.130, 0.139, 0.169, 0.164, 0.175, | |
| 0.135, 0.152, 0.169, NaN, 0.132, 0.167, 0.139, 0.184, 0.159, 0.140, | |
| 0.146, 0.157, NaN, 0.139, 0.183, 0.160, 0.143 | |
| ]; | |
| var svg = d3.select("svg"), | |
| margin = {top: 0, right: 0, bottom: 0, left: 0}, | |
| width = svg.attr("width") - margin.left - margin.right, | |
| height = svg.attr("height") - margin.top - margin.bottom, | |
| padding = 3; | |
| var projection = d3.geoAlbersUsa(); | |
| var radius = d3.scaleSqrt() | |
| .domain([0, d3.max(valueById)]) | |
| .range([0, 30]); | |
| d3.json("us-state-centroids.json", function(error, states) { | |
| if (error) throw error; | |
| var nodes = states.features | |
| .filter(function(d) { return !isNaN(valueById[+d.id]); }) | |
| .map(function(d) { | |
| var point = projection(d.geometry.coordinates), | |
| value = valueById[+d.id]; | |
| if (isNaN(value)) fail(); | |
| return { | |
| x: point[0], y: point[1], | |
| x0: point[0], y0: point[1], | |
| r: radius(value), | |
| value: value | |
| }; | |
| }); | |
| var simulation = d3.forceSimulation() | |
| .force("x", d3.forceX(function(d) { return d.x0; })) | |
| .force("y", d3.forceY(function(d) { return d.y0; })) | |
| .force("collide", collide) | |
| .nodes(nodes) | |
| .on("tick", tick); | |
| var node = svg.selectAll("rect") | |
| .data(nodes) | |
| .enter().append("rect") | |
| .attr("width", function(d) { return d.r * 2; }) | |
| .attr("height", function(d) { return d.r * 2; }); | |
| function tick(e) { | |
| node.attr("x", function(d) { return d.x - d.r; }) | |
| .attr("y", function(d) { return d.y - d.r; }); | |
| } | |
| function collide() { | |
| for (var k = 0, iterations = 4, strength = 0.5; k < iterations; ++k) { | |
| for (var i = 0, n = nodes.length; i < n; ++i) { | |
| for (var a = nodes[i], j = i + 1; j < n; ++j) { | |
| var b = nodes[j], | |
| x = a.x + a.vx - b.x - b.vx, | |
| y = a.y + a.vy - b.y - b.vy, | |
| lx = Math.abs(x), | |
| ly = Math.abs(y), | |
| r = a.r + b.r + padding; | |
| if (lx < r && ly < r) { | |
| if (lx > ly) { | |
| lx = (lx - r) * (x < 0 ? -strength : strength); | |
| a.vx -= lx, b.vx += lx; | |
| } else { | |
| ly = (ly - r) * (y < 0 ? -strength : strength); | |
| a.vy -= ly, b.vy += ly; | |
| } | |
| } | |
| } | |
| } | |
| } | |
| } | |
| }); | |
| </script> |
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