Merge branch 'greatcircle' of https://github.com/jasondavies/d3 into …

…release

Makefile

@@ -185,6 +185,7 @@ d3.geo.js: \
 	src/geo/mercator.js \
 	src/geo/path.js \
 	src/geo/bounds.js \
+	src/geo/greatCircle.js \
 	src/end.js
 
 d3.csv.js: \

d3.geo.js

@@ -564,4 +564,95 @@ function d3_geo_boundsPolygon(o, f) {
     f.apply(null, a[i]);
   }
 }
+// From http://williams.best.vwh.net/avform.htm#Intermediate
+d3.geo.greatCircle = function() {
+  var source = d3_geo_greatCircleSource,
+      target = d3_geo_greatCircleTarget,
+      n = 100,
+      radius = 6371; // Mean radius of Earth, in km.
+  // TODO: breakAtDateLine?
+
+  function greatCircle(d, i) {
+    var from = source.call(this, d, i),
+        to = target.call(this, d, i),
+        x0 = from[0] * d3_radians,
+        y0 = from[1] * d3_radians,
+        x1 = to[0] * d3_radians,
+        y1 = to[1] * d3_radians,
+        cx0 = Math.cos(x0), sx0 = Math.sin(x0),
+        cy0 = Math.cos(y0), sy0 = Math.sin(y0),
+        cx1 = Math.cos(x1), sx1 = Math.sin(x1),
+        cy1 = Math.cos(y1), sy1 = Math.sin(y1),
+        d = Math.acos(sy0 * sy1 + cy0 * cy1 * Math.cos(x1 - x0)),
+        sd = Math.sin(d),
+        f = d / (n - 1),
+        e = -f,
+        path = [],
+        i = -1;
+
+    while (++i < n) {
+      e += f;
+      var A = Math.sin(d - e) / sd,
+          B = Math.sin(e) / sd,
+          x = A * cy0 * cx0 + B * cy1 * cx1,
+          y = A * cy0 * sx0 + B * cy1 * sx1,
+          z = A * sy0       + B * sy1;
+      path[i] = [
+        Math.atan2(y, x) / d3_radians,
+        Math.atan2(z, Math.sqrt(x * x + y * y)) / d3_radians
+      ];
+    }
+
+    return path;
+  }
+
+  greatCircle.source = function(x) {
+    if (!arguments.length) return source;
+    source = x;
+    return greatCircle;
+  };
+
+  greatCircle.target = function(x) {
+    if (!arguments.length) return target;
+    target = x;
+    return greatCircle;
+  };
+
+  greatCircle.n = function(x) {
+    if (!arguments.length) return n;
+    n = +x;
+    return greatCircle;
+  };
+
+  greatCircle.radius = function(x) {
+    if (!arguments.length) return radius;
+    radius = +x;
+    return greatCircle;
+  };
+
+  // Haversine formula for great-circle distance.
+  greatCircle.distance = function(d, i) {
+    var from = source.call(this, d, i),
+        to = target.call(this, d, i),
+        x0 = from[0] * d3_radians,
+        y0 = from[1] * d3_radians,
+        x1 = to[0] * d3_radians,
+        y1 = to[1] * d3_radians,
+        sy = Math.sin((y1 - y0) / 2),
+        sx = Math.sin((x1 - x0) / 2),
+        a = sy * sy + Math.cos(y0) * Math.cos(y1) * sx * sx;
+
+    return radius * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+  };
+
+  return greatCircle;
+};
+
+function d3_geo_greatCircleSource(d) {
+  return d.source;
+}
+
+function d3_geo_greatCircleTarget(d) {
+  return d.target;
+}
 })();

src/geo/greatCircle.js

@@ -0,0 +1,91 @@
+// From http://williams.best.vwh.net/avform.htm#Intermediate
+d3.geo.greatCircle = function() {
+  var source = d3_geo_greatCircleSource,
+      target = d3_geo_greatCircleTarget,
+      n = 100,
+      radius = 6371; // Mean radius of Earth, in km.
+  // TODO: breakAtDateLine?
+
+  function greatCircle(d, i) {
+    var from = source.call(this, d, i),
+        to = target.call(this, d, i),
+        x0 = from[0] * d3_radians,
+        y0 = from[1] * d3_radians,
+        x1 = to[0] * d3_radians,
+        y1 = to[1] * d3_radians,
+        cx0 = Math.cos(x0), sx0 = Math.sin(x0),
+        cy0 = Math.cos(y0), sy0 = Math.sin(y0),
+        cx1 = Math.cos(x1), sx1 = Math.sin(x1),
+        cy1 = Math.cos(y1), sy1 = Math.sin(y1),
+        d = Math.acos(sy0 * sy1 + cy0 * cy1 * Math.cos(x1 - x0)),
+        sd = Math.sin(d),
+        f = d / (n - 1),
+        e = -f,
+        path = [],
+        i = -1;
+
+    while (++i < n) {
+      e += f;
+      var A = Math.sin(d - e) / sd,
+          B = Math.sin(e) / sd,
+          x = A * cy0 * cx0 + B * cy1 * cx1,
+          y = A * cy0 * sx0 + B * cy1 * sx1,
+          z = A * sy0       + B * sy1;
+      path[i] = [
+        Math.atan2(y, x) / d3_radians,
+        Math.atan2(z, Math.sqrt(x * x + y * y)) / d3_radians
+      ];
+    }
+
+    return path;
+  }
+
+  greatCircle.source = function(x) {
+    if (!arguments.length) return source;
+    source = x;
+    return greatCircle;
+  };
+
+  greatCircle.target = function(x) {
+    if (!arguments.length) return target;
+    target = x;
+    return greatCircle;
+  };
+
+  greatCircle.n = function(x) {
+    if (!arguments.length) return n;
+    n = +x;
+    return greatCircle;
+  };
+
+  greatCircle.radius = function(x) {
+    if (!arguments.length) return radius;
+    radius = +x;
+    return greatCircle;
+  };
+
+  // Haversine formula for great-circle distance.
+  greatCircle.distance = function(d, i) {
+    var from = source.call(this, d, i),
+        to = target.call(this, d, i),
+        x0 = from[0] * d3_radians,
+        y0 = from[1] * d3_radians,
+        x1 = to[0] * d3_radians,
+        y1 = to[1] * d3_radians,
+        sy = Math.sin((y1 - y0) / 2),
+        sx = Math.sin((x1 - x0) / 2),
+        a = sy * sy + Math.cos(y0) * Math.cos(y1) * sx * sx;
+
+    return radius * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+  };
+
+  return greatCircle;
+};
+
+function d3_geo_greatCircleSource(d) {
+  return d.source;
+}
+
+function d3_geo_greatCircleTarget(d) {
+  return d.target;
+}

test/geo/greatCircle-test.js

@@ -0,0 +1,42 @@
+require("../env");
+require("../../d3");
+require("../../d3.geo");
+
+var vows = require("vows"),
+    assert = require("assert");
+
+var suite = vows.describe("d3.geo.greatCircle");
+
+suite.addBatch({
+  "greatCircle": {
+    topic: function() {
+      return d3.geo.greatCircle()
+          .n(12);
+    },
+    "distance": function(circle) {
+      assert.equal(circle.distance({source: [0, 0], target: [0, 0]}), 0);
+      assert.inDelta(circle.distance({
+        source: [118 + 24 / 60, 33 + 57 / 60],
+        target: [ 73 + 47 / 60, 40 + 38 / 60]
+      }), 3973, .5);
+    },
+    "geodesic": function(circle) {
+      assert.inDelta(circle({source: [5, 52], target: [-120, 37]}), [
+        [   5,        52      ],
+        [  -3.805036, 57.05083],
+        [ -15.122869, 61.30118],
+        [ -29.396213, 64.34584],
+        [ -46.132729, 65.72409],
+        [ -63.394401, 65.15597],
+        [ -78.854311, 62.76337],
+        [ -91.401599, 58.96701],
+        [-101.190927, 54.21333],
+        [-108.843633, 48.83586],
+        [-114.961152, 43.05231],
+        [-120,        37      ]
+      ], .5);
+    }
+  }
+});
+
+suite.export(module);