Fix #83 - add quantize.thresholds.

README.md

@@ -694,6 +694,10 @@ Equivalent to [*continuous*.tickFormat](#continuous_tickFormat).
 
 Equivalent to [*continuous*.nice](#continuous_nice).
 
+<a name="quantize_thresholds" href="#quantize_thresholds">#</a> <i>quantize</i>.<b>thresholds</b>() [<>](https://github.com/d3/d3-scale/blob/master/src/quantize.js "Source")
+
+Returns the array of computed thresholds within the [domain](#quantize_domain).
+
 <a name="quantize_copy" href="#quantize_copy">#</a> <i>quantize</i>.<b>copy</b>() [<>](https://github.com/d3/d3-scale/blob/master/src/quantize.js "Source")
 
 Returns an exact copy of this scale. Changes to this scale will not affect the returned scale, and vice versa.

src/quantize.js

@@ -42,6 +42,10 @@ export default function quantize() {
     return arguments.length ? (unknown = _, scale) : scale;
   };
 
+  scale.thresholds = function() {
+    return domain.slice();
+  };
+
   scale.copy = function() {
     return quantize()
         .domain([x0, x1])

test/quantize-test.js

@@ -8,13 +8,15 @@ tape("scaleQuantize() has the expected defaults", function(test) {
   var s = scale.scaleQuantize();
   test.deepEqual(s.domain(), [0, 1]);
   test.deepEqual(s.range(), [0, 1]);
+  test.deepEqual(s.thresholds(), [0.5]);
   test.equal(s(0.25), 0);
   test.equal(s(0.75), 1);
   test.end();
 });
 
 tape("quantize(value) maps a number to a discrete value in the range", function(test) {
   var s = scale.scaleQuantize().range([0, 1, 2]);
+  test.deepEqual(s.thresholds(), [1 / 3, 2 / 3]);
   test.equal(s(0.0), 0);
   test.equal(s(0.2), 0);
   test.equal(s(0.4), 1);