Add test for scale.quantize.

d3.js

@@ -2650,8 +2650,8 @@ d3.scale.quantize = function() {
 
   scale.domain = function(x) {
     if (!arguments.length) return [x0, x1];
-    x0 = x[0];
-    x1 = x[1];
+    x0 = +x[0];
+    x1 = +x[x.length - 1];
     kx = range.length / (x1 - x0);
     return scale;
   };

src/scale/quantize.js

@@ -11,8 +11,8 @@ d3.scale.quantize = function() {
 
   scale.domain = function(x) {
     if (!arguments.length) return [x0, x1];
-    x0 = x[0];
-    x1 = x[1];
+    x0 = +x[0];
+    x1 = +x[x.length - 1];
     kx = range.length / (x1 - x0);
     return scale;
   };

test/scale/quantize-test.js

@@ -0,0 +1,69 @@
+require("../env");
+require("../../d3");
+
+var vows = require("vows"),
+    assert = require("assert");
+
+var suite = vows.describe("d3.scale.quantize");
+
+suite.addBatch({
+  "quantize": {
+    topic: function() {
+      return d3.scale.quantize;
+    },
+    "has the default domain [0, 1]": function(quantize) {
+      var x = quantize();
+      assert.deepEqual(x.domain(), [0, 1]);
+      assert.equal(x(.25), 0);
+    },
+    "has the default range [0, 1]": function(quantize) {
+      var x = quantize();
+      assert.deepEqual(x.range(), [0, 1]);
+      assert.equal(x(.75), 1);
+    },
+    "maps a number to a discrete value in the range": function(quantize) {
+      var x = quantize().range([0, 1, 2]);
+      assert.equal(x(0), 0);
+      assert.equal(x(.2), 0);
+      assert.equal(x(.4), 1);
+      assert.equal(x(.6), 1);
+      assert.equal(x(.8), 2);
+      assert.equal(x(1), 2);
+    },
+    "coerces domain to numbers": function(quantize) {
+      var x = quantize().domain(["0", "100"]);
+      assert.strictEqual(x.domain()[0], 0);
+      assert.strictEqual(x.domain()[1], 100);
+    },
+    "only considers the extent of the domain": function(quantize) {
+      var x = quantize().domain([-1, 0, 100]);
+      assert.deepEqual(x.domain(), [-1, 100]);
+    },
+    "clamps input values to the domain": function(quantize) {
+      var a = {}, b = {}, c = {}, x = quantize().range([a, b, c]);
+      assert.equal(x(-.5), a);
+      assert.equal(x(1.5), c);
+    },
+    "range cardinality determines the degree of quantization": function(quantize) {
+      var x = quantize();
+      assert.inDelta(x.range(d3.range(0, 1.001, .001))(1/3), .333, 1e-6);
+      assert.inDelta(x.range(d3.range(0, 1.01, .01))(1/3), .33, 1e-6);
+      assert.inDelta(x.range(d3.range(0, 1.1, .1))(1/3), .3, 1e-6);
+      assert.inDelta(x.range(d3.range(0, 1.2, .2))(1/3), .4, 1e-6);
+      assert.inDelta(x.range(d3.range(0, 1.25, .25))(1/3), .25, 1e-6);
+      assert.inDelta(x.range(d3.range(0, 1.5, .5))(1/3), .5, 1e-6);
+      assert.inDelta(x.range(d3.range(1))(1/3), 0, 1e-6);
+    },
+    "range values are arbitrary": function(quantize) {
+      var a = {}, b = {}, c = {}, x = quantize().range([a, b, c]);
+      assert.equal(x(0), a);
+      assert.equal(x(.2), a);
+      assert.equal(x(.4), b);
+      assert.equal(x(.6), b);
+      assert.equal(x(.8), c);
+      assert.equal(x(1), c);
+    }
+  }
+});
+
+suite.export(module);