A demo of TopoJSON using a single file that contains county, state and country boundaries. This example uses topojson.mesh to extract separating lines between states and counties from the geometry collections.
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U.S. TopoJSON
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| function albersUsa() { | |
| var lower48 = d3.geo.albers().rotate([96, 0]).center([0, 38]).parallels([29.5, 45.5]), | |
| alaska = d3.geo.albers().rotate([160, 0, -35]).center([45, 44]).parallels([55, 65]), | |
| hawaii = d3.geo.albers().rotate([160, 0]).center([0, 20]).parallels([8, 18]); | |
| function albersUsa(coordinates) { | |
| return projection(coordinates)(coordinates); | |
| } | |
| function projection(point) { | |
| var lon = point[0], lat = point[1]; | |
| return lat > 50 ? alaska : lon < -140 ? hawaii : lower48; | |
| } | |
| albersUsa.point = function(coordinates, context) { | |
| return projection(coordinates).point(coordinates, context); | |
| }; | |
| albersUsa.line = function(coordinates, context) { | |
| return projection(coordinates[0]).line(coordinates, context); | |
| }; | |
| albersUsa.polygon = function(coordinates, context) { | |
| return projection(coordinates[0][0]).polygon(coordinates, context); | |
| }; | |
| albersUsa.scale = function(x) { | |
| if (!arguments.length) return lower48.scale(); | |
| lower48.scale(x); | |
| alaska.scale(x * .35); | |
| hawaii.scale(x); | |
| return albersUsa.translate(lower48.translate()); | |
| }; | |
| albersUsa.translate = function(x) { | |
| var k = lower48.scale(); | |
| if (!arguments.length) { | |
| x = lower48.translate(); | |
| return [x[0] - .007 * k, x[1] - .007 * k]; | |
| } | |
| lower48.translate([x[0] + .0075 * k, x[1] + .0065 * k]); | |
| alaska.translate([x[0] - .307 * k, x[1] + .187 * k]); | |
| hawaii.translate([x[0] - .206 * k, x[1] + .196 * k]); | |
| return albersUsa; | |
| }; | |
| return albersUsa.scale(1056).translate([400, 250]); | |
| } |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| body, | |
| svg { | |
| height: 100%; | |
| margin: 0; | |
| width: 100%; | |
| float: left; | |
| } | |
| path { | |
| fill: none; | |
| stroke-linejoin: round; | |
| } | |
| .land-glow { | |
| fill: #000; | |
| fill-opacity: .1; | |
| filter: url(#glow); | |
| } | |
| .land-fill { | |
| fill: #fff; | |
| } | |
| .state-boundary { | |
| stroke: #ccc; | |
| stroke-width: .70px; | |
| } | |
| .land-fill, | |
| .county-boundary { | |
| stroke: #ccc; | |
| stroke-width: .35px; | |
| } | |
| </style> | |
| <body> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script src="http://d3js.org/topojson.v0.min.js"></script> | |
| <script src="albers-usa.js"></script> | |
| <script> | |
| var width = 800, | |
| height = 500; | |
| var projection = albersUsa(); | |
| var path = d3.geo.path() | |
| .projection(projection); | |
| var svg = d3.select("body").append("svg") | |
| .attr("viewBox", "0 0 " + width + " " + height) | |
| .attr("width", width) | |
| .attr("height", height); | |
| svg.append("filter") | |
| .attr("id", "glow") | |
| .append("feGaussianBlur") | |
| .attr("stdDeviation", 5); | |
| d3.json("../4090846/us.json", function(error, us) { | |
| svg.append("path") // translucent outer glow | |
| .datum(topojson.object(us, us.objects.land)) | |
| .attr("d", path) | |
| .attr("class", "land-glow"); | |
| svg.append("path") // solid white fill | |
| .datum(topojson.object(us, us.objects.land)) | |
| .attr("d", path) | |
| .attr("class", "land-fill"); | |
| svg.append("path") // thin grey stroke for internal county boundaries | |
| .datum(topojson.mesh(us, us.objects.counties, function(a, b) { return a.id !== b.id && (a.id / 1000 | 0) === (b.id / 1000 | 0); })) | |
| .attr("d", path) | |
| .attr("class", "county-boundary"); | |
| svg.append("path") // thick grey stroke for internal state boundaries | |
| .datum(topojson.mesh(us, us.objects.states, function(a, b) { return a.id !== b.id; })) | |
| .attr("d", path) | |
| .attr("class", "state-boundary"); | |
| }); | |
| </script> |
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