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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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| path { | |
| stroke-linejoin: round; | |
| } | |
| .land-glow { | |
| fill-opacity: .2; | |
| filter: url(#blur); | |
| } | |
| .land-fill { | |
| fill: #fff; | |
| } | |
| .state-boundary { | |
| fill: none; | |
| stroke: #777; | |
| stroke-width: .70px; | |
| } | |
| .county-boundary { | |
| fill: none; | |
| } | |
| .land-fill, | |
| .county-boundary { | |
| stroke: #777; | |
| stroke-width: .35px; | |
| } | |
| </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 = 600; | |
| var projection = d3.geo.albersUsa() | |
| .scale(1285) | |
| .translate([width / 2, height / 2]); | |
| var path = d3.geo.path() | |
| .projection(projection); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var defs = svg.append("defs"); | |
| defs.append("filter") | |
| .attr("id", "blur") | |
| .append("feGaussianBlur") | |
| .attr("stdDeviation", 5); | |
| d3.json("/mbostock/raw/4090846/us.json", function(error, us) { | |
| if (error) throw error; | |
| defs.append("path") | |
| .datum(topojson.feature(us, us.objects.land)) | |
| .attr("id", "land") | |
| .attr("d", path); | |
| svg.append("use") | |
| .attr("class", "land-glow") | |
| .attr("xlink:href", "#land"); | |
| svg.append("use") | |
| .attr("class", "land-fill") | |
| .attr("xlink:href", "#land"); | |
| svg.append("path") | |
| .datum(topojson.mesh(us, us.objects.counties, function(a, b) { | |
| return a !== b // a border between two counties | |
| && (a.id === 53000 || b.id === 5300 // where a and b are in puget sound | |
| || a.id % 1000 && b.id % 1000) // or a and b are not in a lake | |
| && !(a.id / 1000 ^ b.id / 1000); // and a and b are in the same state | |
| })) | |
| .attr("class", "county-boundary") | |
| .attr("d", path); | |
| svg.append("path") | |
| .datum(topojson.mesh(us, us.objects.states, function(a, b) { | |
| return a !== b; // a border between two states | |
| })) | |
| .attr("class", "state-boundary") | |
| .attr("d", path); | |
| }); | |
| d3.select(self.frameElement).style("height", height + "px"); | |
| </script> |
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