JavaScriptCollection
diff --git a/‎Makefile‎
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diff --git a/‎d3.v2.js‎
Lines changed: 22 additions & 0 deletions b/‎d3.v2.js‎
Lines changed: 22 additions & 0 deletions
diff --git a/‎d3.v2.min.js‎
Lines changed: 4 additions & 4 deletions b/‎d3.v2.min.js‎
Lines changed: 4 additions & 4 deletions
diff --git a/‎src/scale/threshold.js‎
Lines changed: 28 additions & 0 deletions b/‎src/scale/threshold.js‎
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diff --git a/‎test/scale/threshold-test.js‎
Lines changed: 52 additions & 0 deletions b/‎test/scale/threshold-test.js‎
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@@ -138,6 +138,7 @@ d3.scale.js: \
 	src/scale/category.js \
 	src/scale/quantile.js \
 	src/scale/quantize.js \
+	src/scale/threshold.js \
 	src/scale/identity.js
 
 d3.svg.js: \
 
@@ -2496,6 +2496,28 @@
     };
     return rescale();
   }
+  d3.scale.threshold = function() {
+    return d3_scale_threshold([ .5 ], [ 0, 1 ]);
+  };
+  function d3_scale_threshold(domain, range) {
+    function scale(x) {
+      return range[d3.bisect(domain, x)];
+    }
+    scale.domain = function(_) {
+      if (!arguments.length) return domain;
+      domain = _;
+      return scale;
+    };
+    scale.range = function(_) {
+      if (!arguments.length) return range;
+      range = _;
+      return scale;
+    };
+    scale.copy = function() {
+      return d3_scale_threshold(domain, range);
+    };
+    return scale;
+  }
   d3.scale.identity = function() {
     return d3_scale_identity([ 0, 1 ]);
   };
 
@@ -0,0 +1,28 @@
+d3.scale.threshold = function() {
+  return d3_scale_threshold([.5], [0, 1]);
+};
+
+function d3_scale_threshold(domain, range) {
+
+  function scale(x) {
+    return range[d3.bisect(domain, x)];
+  }
+
+  scale.domain = function(_) {
+    if (!arguments.length) return domain;
+    domain = _;
+    return scale;
+  };
+
+  scale.range = function(_) {
+    if (!arguments.length) return range;
+    range = _;
+    return scale;
+  };
+
+  scale.copy = function() {
+    return d3_scale_threshold(domain, range);
+  };
+
+  return scale;
+};
@@ -0,0 +1,52 @@
+require("../env");
+
+var vows = require("vows"),
+    assert = require("assert");
+
+var suite = vows.describe("d3.scale.threshold");
+
+suite.addBatch({
+  "threshold": {
+    topic: function() {
+      return d3.scale.threshold;
+    },
+    "has the default domain [.5]": function(threshold) {
+      var x = threshold();
+      assert.deepEqual(x.domain(), [.5]);
+      assert.equal(x(.49), 0);
+    },
+    "has the default range [0, 1]": function(threshold) {
+      var x = threshold();
+      assert.deepEqual(x.range(), [0, 1]);
+      assert.equal(x(.50), 1);
+    },
+    "maps a number to a discrete value in the range": function(threshold) {
+      var x = threshold().domain([1/3, 2/3]).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");
+    },
+    "domain values are arbitrary": function(threshold) {
+      var x = threshold().domain(["10", "2"]).range([0, 1, 2]);
+      assert.strictEqual(x.domain()[0], "10");
+      assert.strictEqual(x.domain()[1], "2");
+      assert.equal(x("0"), 0);
+      assert.equal(x("12"), 1);
+      assert.equal(x("3"), 2);
+    },
+    "range values are arbitrary": function(threshold) {
+      var a = {}, b = {}, c = {}, x = threshold().domain([1/3, 2/3]).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);