In this example, some points (in red) have been used to build a quadtree. The tree structure is then used to aggregate the number of points in each quad (counts obtained for the first level are displayed).
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July 17, 2016 22:12
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Quadtree aggregation
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| svg = d3.select 'svg' | |
| width = svg.node().getBoundingClientRect().width | |
| height = svg.node().getBoundingClientRect().height | |
| side = Math.floor(Math.min(width,height)*0.5) | |
| data = [ | |
| [6,6], | |
| [10,10], | |
| [20,20], | |
| [100,0], | |
| [100,10], | |
| [230,75], | |
| [90,130], | |
| [12,210] | |
| ] | |
| quadtree = d3.quadtree() | |
| .extent [[0,0], [side, side]] | |
| .addAll data | |
| qside = quadtree._x1 - quadtree._x0 | |
| # store a counter for the number of elements in each quad | |
| quadtree.visitAfter (n) -> | |
| if not n.length? | |
| n.size = 1 | |
| else | |
| n.size = d3.sum n, (d) -> if d? then d.size else 0 | |
| # VIS | |
| vis = svg.append 'g' | |
| .attrs | |
| transform: "translate(#{(width-qside)/2},#{(height-qside)/2})" | |
| quads = vis.selectAll '.quad' | |
| .data quadtree.root() | |
| enter_quads = quads.enter().append 'g' | |
| .attrs | |
| class: 'quad' | |
| transform: (d,i) -> "translate(#{quadtree._x0 + i%2 * qside/2},#{quadtree._y0 + Math.floor(i/2) * qside/2})" | |
| enter_quads.append 'rect' | |
| .attrs | |
| width: qside/2 | |
| height: qside/2 | |
| fill: (d) -> if d? then '#DDD' else 'white' | |
| enter_quads.filter((d) -> d?).append 'text' | |
| .text (d) -> d.size | |
| .attrs | |
| x: qside/4 | |
| y: qside/4 | |
| dy: '0.35em' | |
| dots = vis.selectAll '.dot' | |
| .data data | |
| dots.enter().append 'circle' | |
| .attrs | |
| class: 'dot' | |
| cx: (d) -> d[0] | |
| cy: (d) -> d[1] | |
| r: 2 | |
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| body, html { | |
| padding: 0; | |
| margin: 0; | |
| height: 100%; | |
| } | |
| svg { | |
| width: 100%; | |
| height: 100%; | |
| background: white; | |
| } | |
| .quad rect { | |
| stroke: #555; | |
| shape-rendering: crispEdges; | |
| } | |
| .quad text { | |
| font-family: sans-serif; | |
| font-size: 64px; | |
| fill-opacity: 0.2; | |
| text-anchor: middle; | |
| } | |
| .dot { | |
| fill: red; | |
| fill-opacity: 0.2; | |
| stroke: #333; | |
| } |
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>Quadtree aggregation</title> | |
| <link type="text/css" href="index.css" rel="stylesheet"/> | |
| <script src="https://d3js.org/d3.v4.min.js"></script> | |
| <script src="https://d3js.org/d3-selection-multi.v0.4.min.js"></script> | |
| </head> | |
| <body> | |
| <svg></svg> | |
| <script src="index.js"></script> | |
| </body> | |
| </html> |
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| // Generated by CoffeeScript 1.10.0 | |
| (function() { | |
| var data, dots, enter_quads, height, qside, quads, quadtree, side, svg, vis, width; | |
| svg = d3.select('svg'); | |
| width = svg.node().getBoundingClientRect().width; | |
| height = svg.node().getBoundingClientRect().height; | |
| side = Math.floor(Math.min(width, height) * 0.5); | |
| data = [[6, 6], [10, 10], [20, 20], [100, 0], [100, 10], [230, 75], [90, 130], [12, 210]]; | |
| quadtree = d3.quadtree().extent([[0, 0], [side, side]]).addAll(data); | |
| qside = quadtree._x1 - quadtree._x0; | |
| quadtree.visitAfter(function(n) { | |
| if (n.length == null) { | |
| return n.size = 1; | |
| } else { | |
| return n.size = d3.sum(n, function(d) { | |
| if (d != null) { | |
| return d.size; | |
| } else { | |
| return 0; | |
| } | |
| }); | |
| } | |
| }); | |
| vis = svg.append('g').attrs({ | |
| transform: "translate(" + ((width - qside) / 2) + "," + ((height - qside) / 2) + ")" | |
| }); | |
| quads = vis.selectAll('.quad').data(quadtree.root()); | |
| enter_quads = quads.enter().append('g').attrs({ | |
| "class": 'quad', | |
| transform: function(d, i) { | |
| return "translate(" + (quadtree._x0 + i % 2 * qside / 2) + "," + (quadtree._y0 + Math.floor(i / 2) * qside / 2) + ")"; | |
| } | |
| }); | |
| enter_quads.append('rect').attrs({ | |
| width: qside / 2, | |
| height: qside / 2, | |
| fill: function(d) { | |
| if (d != null) { | |
| return '#DDD'; | |
| } else { | |
| return 'white'; | |
| } | |
| } | |
| }); | |
| enter_quads.filter(function(d) { | |
| return d != null; | |
| }).append('text').text(function(d) { | |
| return d.size; | |
| }).attrs({ | |
| x: qside / 4, | |
| y: qside / 4, | |
| dy: '0.35em' | |
| }); | |
| dots = vis.selectAll('.dot').data(data); | |
| dots.enter().append('circle').attrs({ | |
| "class": 'dot', | |
| cx: function(d) { | |
| return d[0]; | |
| }, | |
| cy: function(d) { | |
| return d[1]; | |
| }, | |
| r: 2 | |
| }); | |
| }).call(this); |
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