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Add d3.geo.albersUsa.invert.
1 parent 4648db5 commit 4ce9bff

5 files changed

Lines changed: 105 additions & 10 deletions

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‎d3.js‎

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Original file line numberDiff line numberDiff line change
@@ -5475,13 +5475,17 @@ d3 = function() {
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var alaska = d3.geo.albers().rotate([ 160, 0 ]).center([ 0, 60 ]).parallels([ 55, 65 ]);
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var hawaii = d3.geo.albers().rotate([ 160, 0 ]).center([ 0, 20 ]).parallels([ 8, 18 ]);
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var puertoRico = d3.geo.albers().rotate([ 60, 0 ]).center([ 0, 10 ]).parallels([ 8, 18 ]);
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var alaskaInvert, hawaiiInvert, puertoRicoInvert;
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function albersUsa(coordinates) {
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return projection(coordinates)(coordinates);
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}
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function projection(point) {
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var lon = point[0], lat = point[1];
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return lat > 50 ? alaska : lon < -140 ? hawaii : lat < 21 ? puertoRico : lower48;
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}
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albersUsa.invert = function(coordinates) {
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return alaskaInvert(coordinates) || hawaiiInvert(coordinates) || puertoRicoInvert(coordinates) || lower48.invert(coordinates);
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};
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albersUsa.scale = function(x) {
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if (!arguments.length) return lower48.scale();
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lower48.scale(x);
@@ -5497,10 +5501,25 @@ d3 = function() {
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alaska.translate([ dx - .4 * dz, dy + .17 * dz ]);
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hawaii.translate([ dx - .19 * dz, dy + .2 * dz ]);
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puertoRico.translate([ dx + .58 * dz, dy + .43 * dz ]);
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alaskaInvert = d3_geo_albersUsaInvert(alaska, [ [ -180, 50 ], [ -130, 72 ] ]);
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hawaiiInvert = d3_geo_albersUsaInvert(hawaii, [ [ -164, 18 ], [ -154, 24 ] ]);
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puertoRicoInvert = d3_geo_albersUsaInvert(puertoRico, [ [ -67.5, 17.5 ], [ -65, 19 ] ]);
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return albersUsa;
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};
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return albersUsa.scale(lower48.scale());
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};
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function d3_geo_albersUsaInvert(projection, extent) {
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var a = projection(extent[0]), b = projection([ .5 * (extent[0][0] + extent[1][0]), extent[0][1] ]), c = projection([ extent[1][0], extent[0][1] ]), d = projection(extent[1]);
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var dya = b[1] - a[1], dxa = b[0] - a[0], dyb = c[1] - b[1], dxb = c[0] - b[0];
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var ma = dya / dxa, mb = dyb / dxb;
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var cx = .5 * (ma * mb * (a[1] - c[1]) + mb * (a[0] + b[0]) - ma * (b[0] + c[0])) / (mb - ma), cy = (.5 * (a[0] + b[0]) - cx) / ma + .5 * (a[1] + b[1]);
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var dx0 = d[0] - cx, dy0 = d[1] - cy, dx1 = a[0] - cx, dy1 = a[1] - cy, r0 = dx0 * dx0 + dy0 * dy0, r1 = dx1 * dx1 + dy1 * dy1;
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var a0 = Math.atan2(dy0, dx0), a1 = Math.atan2(dy1, dx1);
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return function(coordinates) {
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var dx = coordinates[0] - cx, dy = coordinates[1] - cy, r = dx * dx + dy * dy, a = Math.atan2(dy, dx);
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if (r0 < r && r < r1 && a0 < a && a < a1) return projection.invert(coordinates);
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};
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}
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function d3_geo_albers(φ0, φ1) {
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var sinφ0 = Math.sin(φ0), n = (sinφ0 + Math.sin(φ1)) / 2, C = 1 + sinφ0 * (2 * n - sinφ0), ρ0 = Math.sqrt(C) / n;
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function albers(λ, φ) {

‎d3.min.js‎

Lines changed: 4 additions & 4 deletions
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‎src/geo/albers-usa.js‎

Lines changed: 53 additions & 3 deletions
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@@ -1,6 +1,4 @@
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// TODO composite invert
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// A composite projection for the United States, 960x500. The set of standard
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// A composite projection for the United States, 960×500. The set of standard
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// parallels for each region comes from USGS, which is published here:
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// http://egsc.usgs.gov/isb/pubs/MapProjections/projections.html#albers
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d3.geo.albersUsa = function() {
@@ -21,6 +19,10 @@ d3.geo.albersUsa = function() {
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.center([0, 10])
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.parallels([8, 18]);
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var alaskaInvert,
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hawaiiInvert,
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puertoRicoInvert;
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function albersUsa(coordinates) {
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return projection(coordinates)(coordinates);
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}
@@ -34,6 +36,10 @@ d3.geo.albersUsa = function() {
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: lower48;
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}
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albersUsa.invert = function(coordinates) {
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return alaskaInvert(coordinates) || hawaiiInvert(coordinates) || puertoRicoInvert(coordinates) || lower48.invert(coordinates);
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};
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albersUsa.scale = function(x) {
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if (!arguments.length) return lower48.scale();
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lower48.scale(x);
@@ -52,8 +58,52 @@ d3.geo.albersUsa = function() {
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alaska.translate([dx - .40 * dz, dy + .17 * dz]);
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hawaii.translate([dx - .19 * dz, dy + .20 * dz]);
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puertoRico.translate([dx + .58 * dz, dy + .43 * dz]);
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alaskaInvert = d3_geo_albersUsaInvert(alaska, [[-180, 50], [-130, 72]]);
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hawaiiInvert = d3_geo_albersUsaInvert(hawaii, [[-164, 18], [-154, 24]]);
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puertoRicoInvert = d3_geo_albersUsaInvert(puertoRico, [[-67.5, 17.5], [-65, 19]]);
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return albersUsa;
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};
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return albersUsa.scale(lower48.scale());
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};
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function d3_geo_albersUsaInvert(projection, extent) {
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var a = projection(extent[0]),
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b = projection([.5 * (extent[0][0] + extent[1][0]), extent[0][1]]),
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c = projection([extent[1][0], extent[0][1]]),
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d = projection(extent[1]);
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var dya = b[1]- a[1],
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dxa = b[0]- a[0],
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dyb = c[1]- b[1],
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dxb = c[0]- b[0];
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var ma = dya / dxa,
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mb = dyb / dxb;
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// Find center of circle going through points [a, b, c].
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var cx = .5 * (ma * mb * (a[1] - c[1]) + mb * (a[0] + b[0]) - ma * (b[0] + c[0])) / (mb - ma),
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cy = (.5 * (a[0] + b[0]) - cx) / ma + .5 * (a[1] + b[1]);
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// Radial distance² from center.
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var dx0 = d[0] - cx,
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dy0 = d[1] - cy,
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dx1 = a[0] - cx,
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dy1 = a[1] - cy,
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r0 = dx0 * dx0 + dy0 * dy0,
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r1 = dx1 * dx1 + dy1 * dy1;
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// Angular extent.
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var a0 = Math.atan2(dy0, dx0),
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a1 = Math.atan2(dy1, dx1);
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return function(coordinates) {
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var dx = coordinates[0] - cx,
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dy = coordinates[1] - cy,
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r = dx * dx + dy * dy,
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a = Math.atan2(dy, dx);
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if (r0 < r && r < r1 && a0 < a && a < a1) return projection.invert(coordinates);
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};
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}

‎test/geo/albers-test.js‎

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@@ -7,9 +7,7 @@ var suite = vows.describe("d3.geo.albers");
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suite.addBatch({
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"albers": {
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topic: function() {
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return d3.geo.albers();
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},
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topic: d3.geo.albers,
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"Arctic": function(albers) {
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var coords = albers([0, 85]);
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assert.inDelta(coords[0], 1031.393796, 1e-6);

‎test/geo/albers-usa-test.js‎

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@@ -0,0 +1,28 @@
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require("../env");
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var vows = require("vows"),
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assert = require("assert");
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var suite = vows.describe("d3.geo.albersUsa");
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suite.addBatch({
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"albersUsa": {
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topic: d3.geo.albersUsa,
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"Washington": equalInverse([-120.5, 47.5], [215.478997, 51.976493]),
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"San Francisco": equalInverse([-122.42, 37.78], [150.072677, 211.257829]),
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"Juneau, Alaska": equalInverse([-134.22, 58.43], [217.366590, 409.498517]),
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"Honolulu, Hawaii": equalInverse([-157.82, 21.30], [325.696002, 427.278824]),
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"San Juan, Puerto Rico": equalInverse([-66.07, 18.45], [909.159250, 456.394827])
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}
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});
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suite.export(module);
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function equalInverse(location, point) {
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return function(projection) {
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var projected;
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assert.inDelta(projected = projection(location), point, 1e-6);
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assert.inDelta(projection.invert(projected), location, 1e-6);
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assert.inDelta(projection(projection.invert(point)), point, 1e-6);
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};
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};

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