Add band/point invert.

d3 · May 27, 2016 · b78edc3 · b78edc3
1 parent e81238b
commit b78edc3
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Showing 2 changed files with 115 additions and 1 deletion.
diff --git a/src/band.js b/src/band.js
@@ -1,4 +1,4 @@
-import {range as sequence} from "d3-array";
+import {range as sequence, bisectRight} from "d3-array";
 import ordinal from "./ordinal";
 
 export default function band() {
@@ -69,6 +69,28 @@ export default function band() {
     return arguments.length ? (align = Math.max(0, Math.min(1, _)), rescale()) : align;
   };
 
+  scale.invert = function(x, y) {
+    var lo = +x,
+        hi = arguments.length > 1 ? +y : lo,
+        reverse = range[1] < range[0],
+        values = reverse ? ordinalRange().reverse() : ordinalRange(),
+        n = values.length - 1, a, b, t;
+
+    // order range inputs, bail if outside of scale range
+    if (hi < lo) t = lo, lo = hi, hi = t;
+    if (hi < values[0] || lo > range[1-reverse]) return undefined;
+
+    // binary search to index into scale range
+    a = Math.max(0, bisectRight(values, lo) - 1);
+    b = lo===hi ? a : bisectRight(values, hi) - 1;
+
+    // increment index a if lo is within padding gap
+    if (lo - values[a] > bandwidth + 1e-10) ++a;
+
+    if (reverse) t = a, a = n - b, b = n - t; // map + swap
+    return (a > b) ? undefined : domain().slice(a, b+1);
+  };
+
   scale.copy = function() {
     return band()
         .domain(domain())

diff --git a/test/band-test.js b/test/band-test.js
@@ -252,4 +252,96 @@ tape("band.copy() isolates changes to the range", function(test) {
   test.end();
 });
 
+tape("band.invert(x) inverts single value", function(test) {
+  var s = scale.scaleBand().domain(["foo", "bar"]);
+
+  // ascending range
+  s.range([0,2]);
+  test.deepEqual(s.invert(-1),  undefined);
+  test.deepEqual(s.invert(0.0), ["foo"]);
+  test.deepEqual(s.invert(0.5), ["foo"]);
+  test.deepEqual(s.invert(1.0), ["bar"]);
+  test.deepEqual(s.invert(1.5), ["bar"]);
+  test.deepEqual(s.invert(2.0), ["bar"]);
+  test.deepEqual(s.invert(2.1), undefined);
+
+  // ascending range with padding
+  s.padding(0.3);
+  test.deepEqual(s.invert(-1),  undefined);
+  test.deepEqual(s.invert(0.0), undefined);
+  test.deepEqual(s.invert(0.5), ["foo"]);
+  test.deepEqual(s.invert(1.0), undefined);
+  test.deepEqual(s.invert(1.5), ["bar"]);
+  test.deepEqual(s.invert(2.0), undefined);
+  test.deepEqual(s.invert(2.1), undefined);
+
+  // descending range
+  s.padding(0).range([2, 0]);
+  test.deepEqual(s.invert(-1),  undefined);
+  test.deepEqual(s.invert(0.0), ["bar"]);
+  test.deepEqual(s.invert(0.5), ["bar"]);
+  test.deepEqual(s.invert(1.0), ["foo"]);
+  test.deepEqual(s.invert(1.5), ["foo"]);
+  test.deepEqual(s.invert(2.0), ["foo"]);
+  test.deepEqual(s.invert(2.1), undefined);
+
+  // descending range with padding
+  s.padding(0.3);
+  test.deepEqual(s.invert(-1),  undefined);
+  test.deepEqual(s.invert(0.0), undefined);
+  test.deepEqual(s.invert(0.5), ["bar"]);
+  test.deepEqual(s.invert(1.0), undefined);
+  test.deepEqual(s.invert(1.5), ["foo"]);
+  test.deepEqual(s.invert(2.0), undefined);
+  test.deepEqual(s.invert(2.1), undefined);
+
+  test.end();
+});
+
+tape("band.invert(x) inverts value range", function(test) {
+  var s = scale.scaleBand().domain(["foo", "bar"]);
+
+  // ascending range
+  s.range([0, 2]);
+  test.deepEqual(s.invert(-2, -1), undefined);
+  test.deepEqual(s.invert(-1, 0),  ["foo"]);
+  test.deepEqual(s.invert(0, 0.5), ["foo"]);
+  test.deepEqual(s.invert(0, 1),   ["foo", "bar"]);
+  test.deepEqual(s.invert(0, 2),   ["foo", "bar"]);
+  test.deepEqual(s.invert(2, 3),   ["bar"]);
+  test.deepEqual(s.invert(3, 4),   undefined);
+
+  // ascending range with padding
+  s.padding(0.3);
+  test.deepEqual(s.invert( -1,   0),  undefined);
+  test.deepEqual(s.invert(0.0, 0.1),  undefined);
+  test.deepEqual(s.invert(0.0, 0.5), ["foo"]);
+  test.deepEqual(s.invert(0.5, 1.5), ["foo", "bar"]);
+  test.deepEqual(s.invert(0.9, 1.1), undefined);
+  test.deepEqual(s.invert(1.0, 1.5), ["bar"]);
+  test.deepEqual(s.invert(1.9, 2.0), undefined);
+
+  // descending range
+  s.padding(0).range([2, 0]);
+  test.deepEqual(s.invert(-2, -1), undefined);
+  test.deepEqual(s.invert(-1, 0),  ["bar"]);
+  test.deepEqual(s.invert(0, 0.5), ["bar"]);
+  test.deepEqual(s.invert(0, 1),   ["foo", "bar"]);
+  test.deepEqual(s.invert(0, 2),   ["foo", "bar"]);
+  test.deepEqual(s.invert(2, 3),   ["foo"]);
+  test.deepEqual(s.invert(3, 4),   undefined);
+
+  // descending range with padding
+  s.padding(0.3);
+  test.deepEqual(s.invert( -1, 0.0),  undefined);
+  test.deepEqual(s.invert(0.0, 0.1),  undefined);
+  test.deepEqual(s.invert(0.0, 0.5), ["bar"]);
+  test.deepEqual(s.invert(0.5, 1.5), ["foo", "bar"]);
+  test.deepEqual(s.invert(0.9, 1.1), undefined);
+  test.deepEqual(s.invert(1.0, 1.5), ["foo"]);
+  test.deepEqual(s.invert(1.9, 2.0), undefined);
+
+  test.end();
+});
+
 // TODO align tests for padding & round