Optional search radius.

README.md

@@ -112,9 +112,9 @@ Returns an array of all data in the quadtree.
 
 Returns the total number of data in the quadtree.
 
-<a name="quadtree_find" href="#quadtree_find">#</a> <i>quadtree</i>.<b>find</b>(<i>x</i>, <i>y</i>)
+<a name="quadtree_find" href="#quadtree_find">#</a> <i>quadtree</i>.<b>find</b>(<i>x</i>, <i>y</i>[, <i>radius</i>])
 
-Given a point ⟨*x*,*y*⟩, returns the closest datum in the quadtree. If the quadtree is empty, returns undefined.
+Returns the datum closest to the position ⟨*x*,*y*⟩ with the given search *radius*. If *radius* is not specified, it defaults to infinity. If there is no datum within the search area, returns undefined.
 
 <a name="quadtree_visit" href="#quadtree_visit">#</a> <i>quadtree</i>.<b>visit</b>(<i>callback</i>)
 

src/find.js

@@ -1,8 +1,7 @@
 import Quad from "./quad";
 
-export default function(x, y) {
-  var minDistance2 = Infinity,
-      minPoint,
+export default function(x, y, radius) {
+  var data,
       x0 = this._x0,
       y0 = this._y0,
       x1,
@@ -17,6 +16,12 @@ export default function(x, y) {
       i;
 
   if (node) quads.push(new Quad(node, x0, y0, x3, y3));
+  if (radius == null) radius = Infinity;
+  else {
+    x0 = x - radius, y0 = y - radius;
+    x3 = x + radius, y3 = y + radius;
+    radius *= radius;
+  }
 
   while (q = quads.pop()) {
 
@@ -52,14 +57,14 @@ export default function(x, y) {
       var dx = x - +this._x.call(null, node.data),
           dy = y - +this._y.call(null, node.data),
           d2 = dx * dx + dy * dy;
-      if (d2 < minDistance2) {
-        var d = Math.sqrt(minDistance2 = d2);
+      if (d2 < radius) {
+        var d = Math.sqrt(radius = d2);
         x0 = x - d, y0 = y - d;
         x3 = x + d, y3 = y + d;
-        minPoint = node.data;
+        data = node.data;
       }
     }
   }
 
-  return minPoint;
+  return data;
 }

test/find-test.js

@@ -13,3 +13,22 @@ tape("quadtree.find(x, y) returns the closest point to the given [x, y]", functi
   test.deepEqual(q.find(15.9, 15.9), [16, 16]);
   test.end();
 });
+
+tape("quadtree.find(x, y, radius) returns the closest point within the search radius to the given [x, y]", function(test) {
+  var q = d3_quadtree.quadtree([[0, 0], [100, 0], [0, 100], [100, 100]]);
+  test.deepEqual(q.find(20, 20, Infinity), [0, 0]);
+  test.deepEqual(q.find(20, 20, 20 * Math.SQRT2 + 1e-6), [0, 0]);
+  test.equal(q.find(20, 20, 20 * Math.SQRT2 - 1e-6), undefined);
+  test.deepEqual(q.find(0, 20, 20 + 1e-6), [0, 0]);
+  test.equal(q.find(0, 20, 20 - 1e-6), undefined);
+  test.deepEqual(q.find(20, 0, 20 + 1e-6), [0, 0]);
+  test.equal(q.find(20, 0, 20 - 1e-6), undefined);
+  test.end();
+});
+
+tape("quadtree.find(x, y, null) treats the given radius as Infinity", function(test) {
+  var q = d3_quadtree.quadtree([[0, 0], [100, 0], [0, 100], [100, 100]]);
+  test.deepEqual(q.find(20, 20, null), [0, 0]);
+  test.deepEqual(q.find(20, 20, undefined), [0, 0]);
+  test.end();
+});