Step 2 of 4 of topology construction. From How To Infer Topology.
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Junction Finding
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| license: gpl-3.0 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| .mesh { | |
| fill: none; | |
| stroke: #333; | |
| stroke-width: .5px; | |
| stroke-linejoin: round; | |
| } | |
| .junction { | |
| fill: black; | |
| stroke: white; | |
| } | |
| </style> | |
| <body> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script src="//d3js.org/topojson.v1.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500; | |
| var path = d3.geo.path() | |
| .projection(null); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("us.json", function(error, us) { | |
| if (error) throw error; | |
| svg.append("path") | |
| .datum(topojson.mesh(us)) | |
| .attr("class", "mesh") | |
| .attr("d", path); | |
| var junctionByPoint = d3.map(), | |
| arcCountsByPoint = d3.map(); | |
| us.arcs.forEach(function(arc) { | |
| var start = arc[0], | |
| startCount = arcCountsByPoint.get(start) || 0, | |
| end = arc.reduce(function(p, v) { return [p[0] + v[0], p[1] + v[1]]; }), | |
| endCount = arcCountsByPoint.get(end) || 0; | |
| if (arcCountsByPoint.set(start, startCount + 1) > 1) junctionByPoint.set(start, start); | |
| if (arcCountsByPoint.set(end, endCount + 1) > 1) junctionByPoint.set(end, end); | |
| }); | |
| svg.selectAll(".junction") | |
| .data(junctionByPoint.values()) | |
| .enter().append("circle") | |
| .attr("class", "junction") | |
| .attr("transform", function(d) { return "translate(" + transform(d) + ")"; }) | |
| .attr("r", 2.5); | |
| function transform(point) { | |
| return [ | |
| point[0] * us.transform.scale[0] + us.transform.translate[0], | |
| point[1] * us.transform.scale[1] + us.transform.translate[1] | |
| ]; | |
| } | |
| }); | |
| </script> |
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