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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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <title>Demers Cartogram</title> | |
| <style> | |
| rect { | |
| fill: #eee; | |
| stroke: #000; | |
| stroke-width: 1.5px; | |
| } | |
| </style> | |
| <body> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script> | |
| // Ratio of Obese (BMI >= 30) in U.S. Adults, CDC 2008 | |
| var valueById = [ | |
| NaN, .187, .198, NaN, .133, .175, .151, NaN, .100, .125, | |
| .171, NaN, .172, .133, NaN, .108, .142, .167, .201, .175, | |
| .159, .169, .177, .141, .163, .117, .182, .153, .195, .189, | |
| .134, .163, .133, .151, .145, .130, .139, .169, .164, .175, | |
| .135, .152, .169, NaN, .132, .167, .139, .184, .159, .140, | |
| .146, .157, NaN, .139, .183, .160, .143 | |
| ]; | |
| var margin = {top: 0, right: 0, bottom: 0, left: 0}, | |
| width = 960 - margin.left - margin.right, | |
| height = 500 - margin.top - margin.bottom, | |
| padding = 3; | |
| var projection = d3.geo.albersUsa(); | |
| var radius = d3.scale.sqrt() | |
| .domain([0, d3.max(valueById)]) | |
| .range([0, 30]); | |
| var force = d3.layout.force() | |
| .charge(0) | |
| .gravity(0) | |
| .size([width, height]); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("/mbostock/raw/3750900/us-state-centroids.json", function(error, states) { | |
| var nodes = states.features | |
| .filter(function(d) { return !isNaN(valueById[+d.id]); }) | |
| .map(function(d) { | |
| var point = projection(d.geometry.coordinates), | |
| value = .1; | |
| if (isNaN(value)) fail(); | |
| return { | |
| x: point[0], y: point[1], | |
| x0: point[0], y0: point[1], | |
| r: radius(value), | |
| value: value | |
| }; | |
| }); | |
| force | |
| .nodes(nodes) | |
| .on("tick", tick) | |
| .start(); | |
| 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.each(gravity(e.alpha * .1)) | |
| .each(collide(.5)) | |
| .attr("x", function(d) { return d.x - d.r; }) | |
| .attr("y", function(d) { return d.y - d.r; }); | |
| } | |
| function gravity(k) { | |
| return function(d) { | |
| d.x += (d.x0 - d.x) * k; | |
| d.y += (d.y0 - d.y) * k; | |
| }; | |
| } | |
| function collide(k) { | |
| var q = d3.geom.quadtree(nodes); | |
| return function(node) { | |
| var nr = node.r + padding, | |
| nx1 = node.x - nr, | |
| nx2 = node.x + nr, | |
| ny1 = node.y - nr, | |
| ny2 = node.y + nr; | |
| q.visit(function(quad, x1, y1, x2, y2) { | |
| if (quad.point && (quad.point !== node)) { | |
| var x = node.x - quad.point.x, | |
| y = node.y - quad.point.y, | |
| lx = Math.abs(x), | |
| ly = Math.abs(y), | |
| r = nr + quad.point.r; | |
| if (lx < r && ly < r) { | |
| if (lx > ly) { | |
| lx = (lx - r) * (x < 0 ? -k : k); | |
| node.x -= lx; | |
| quad.point.x += lx; | |
| } else { | |
| ly = (ly - r) * (y < 0 ? -k : k); | |
| node.y -= ly; | |
| quad.point.y += ly; | |
| } | |
| } | |
| } | |
| return x1 > nx2 || x2 < nx1 || y1 > ny2 || y2 < ny1; | |
| }); | |
| }; | |
| } | |
| }); | |
| </script> |
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