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Last active October 13, 2015 03:47
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Stitching States from Counties
d3.json("us-counties.json", function(error, topology) {
if (error) throw error;
var infoByArc = {},
arcsByState = {};
topology.objects[0].geometries.forEach(function(object) {
object.arcs.forEach(object.type === "MultiPolygon"
? function(polygon) { polygon.forEach(function(ring) { ring.forEach(info); }); }
: function(ring) { ring.forEach(info); });
function info(arc) {
if (arc < 0) arc = ~arc;
var info = infoByArc[arc] || (infoByArc[arc] = {count: 0, states: {}});
info.states[Math.floor(object.id / 1000)] = 1;
++info.count;
}
});
topology.arcs.forEach(function(arc, i) {
var info = infoByArc[arc.index = i];
if (info.count === d3.keys(info.states).length) {
d3.keys(info.states).forEach(function(state) {
(arcsByState[state] || (arcsByState[state] = [])).push(arc);
});
}
});
for (var state in arcsByState) {
var arcs = arcsByState[state],
arcsByEnd = {},
fragmentsByStart = {},
fragmentsByEnd = {};
arcs.forEach(function(arc) {
var e = ends(arc);
(arcsByEnd[e[0]] || (arcsByEnd[e[0]] = [])).push(arc.index);
(arcsByEnd[e[1]] || (arcsByEnd[e[1]] = [])).push(~arc.index);
});
arcs.forEach(function(arc) {
var e = ends(arc),
start = e[0],
end = e[1],
f, g;
if (f = fragmentsByEnd[start]) { // add to end of existing fragment
delete fragmentsByStart[f.start];
delete fragmentsByEnd[f.end];
f.push(arc.index);
f.end = end;
if (g = fragmentsByStart[end]) { // stitch together existing fragments f:g
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var fg = f.concat(g);
fragmentsByStart[fg.start = f.start] = fragmentsByEnd[fg.end = g.end] = fg;
} else if (g = fragmentsByEnd[end]) { // stitch together existing fragments f:~g
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var fg = f.concat(g.map(function(i) { return ~i; }).reverse());
fragmentsByStart[fg.start = f.start] = fragmentsByEnd[fg.end = g.start] = fg;
} else {
fragmentsByStart[f.start] = fragmentsByEnd[f.end] = f;
}
} else if (f = fragmentsByStart[end]) { // add to start of existing fragment
delete fragmentsByStart[f.start];
delete fragmentsByEnd[f.end];
f.unshift(arc.index);
f.start = start;
if (g = fragmentsByEnd[start]) { // stitch together existing fragments g:f
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var gf = g.concat(f);
fragmentsByStart[gf.start = g.start] = fragmentsByEnd[gf.end = f.end] = gf;
} else if (g = fragmentsByStart[start]) { // stitch together existing fragments ~g:f
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var gf = g.map(function(i) { return ~i; }).reverse().concat(f);
fragmentsByStart[gf.start = g.end] = fragmentsByEnd[gf.end = f.end] = gf;
} else {
fragmentsByStart[f.start] = fragmentsByEnd[f.end] = f;
}
} else if (f = fragmentsByStart[start]) { // add reverse to start of existing fragment
delete fragmentsByStart[f.start];
delete fragmentsByEnd[f.end];
f.unshift(~arc.index);
f.start = end;
if (g = fragmentsByEnd[end]) { // stitch together existing fragments g:f
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var gf = g.concat(f);
fragmentsByStart[gf.start = g.start] = fragmentsByEnd[gf.end = f.end] = gf;
} else if (g = fragmentsByStart[end]) { // stitch together existing fragments ~g:f
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var gf = g.map(function(i) { return ~i; }).reverse().concat(f);
fragmentsByStart[gf.start = g.end] = fragmentsByEnd[gf.end = f.end] = gf;
} else {
fragmentsByStart[f.start] = fragmentsByEnd[f.end] = f;
}
} else if (f = fragmentsByEnd[end]) { // add reverse to end of existing fragment
delete fragmentsByStart[f.start];
delete fragmentsByEnd[f.end];
f.push(~arc.index);
f.end = start;
if (g = fragmentsByEnd[start]) { // stitch together existing fragments f:g
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var fg = f.concat(g);
fragmentsByStart[fg.start = f.start] = fragmentsByEnd[fg.end = g.end] = fg;
} else if (g = fragmentsByStart[start]) { // stitch together existing fragments f:~g
delete fragmentsByStart[g.start];
delete fragmentsByEnd[g.end];
var fg = f.concat(g.map(function(i) { return ~i; }).reverse());
fragmentsByStart[fg.start = f.start] = fragmentsByEnd[fg.end = g.start] = fg;
} else {
fragmentsByStart[f.start] = fragmentsByEnd[f.end] = f;
}
} else {
f = [arc.index];
fragmentsByStart[f.start = start] = fragmentsByEnd[f.end = end] = f;
}
});
if (state == 6) {
console.log(fragmentsByEnd);
}
arcs.multiPolygon = d3.values(fragmentsByEnd).map(function(arcs) { return [arcs]; });
arcs.multiLineString = arcs.map(function(arc) { return [arc.index]; });
}
function ends(arc) {
var p0 = arc[0], p1 = [0, 0];
arc.forEach(function(dp) { p1[0] += dp[0], p1[1] += dp[1]; });
return [p0, p1];
}
console.log(arcsByState);
});
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