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@mbostock

mbostock/.block

Last active Sep 12, 2018
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Junction Finding
license: gpl-3.0
<!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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