More efficient degenerate bin check.

d3.v2.js

@@ -5894,12 +5894,14 @@ d3.layout.histogram = function() {
     }
 
     // Fill the bins, ignoring values outside the range.
-    i = -1; while(++i < n) {
-      x = values[i];
-      if ((x >= range[0]) && (x <= range[1])) {
-        bin = bins[d3.bisect(thresholds, x, 1, m) - 1];
-        bin.y += k;
-        bin.push(data[i]);
+    if (m > 0) {
+      i = -1; while(++i < n) {
+        x = values[i];
+        if ((x >= range[0]) && (x <= range[1])) {
+          bin = bins[d3.bisect(thresholds, x, 1, m) - 1];
+          bin.y += k;
+          bin.push(data[i]);
+        }
       }
     }
 

src/layout/histogram.js

@@ -24,11 +24,11 @@ d3.layout.histogram = function() {
     }
 
     // Fill the bins, ignoring values outside the range.
-    i = -1; while(++i < n) {
-      x = values[i];
-      if ((x >= range[0]) && (x <= range[1])) {
-        bin = bins[d3.bisect(thresholds, x, 1, m) - 1];
-        if (bin) {
+    if (m > 0) {
+      i = -1; while(++i < n) {
+        x = values[i];
+        if ((x >= range[0]) && (x <= range[1])) {
+          bin = bins[d3.bisect(thresholds, x, 1, m) - 1];
           bin.y += k;
           bin.push(data[i]);
         }

test/layout/histogram-test.js

@@ -69,8 +69,10 @@ suite.addBatch({
         {x: 2, y: 2, dx: 1}
       ]);
     },
-    "can handle degenerate domain": function(histogram) {
-      var h = histogram().bins(d3.scale.linear().domain([0,0]).ticks(3));
+    "returns the empty array with fewer than two bins": function(histogram) {
+      var h = histogram().bins([1]);
+      assert.deepEqual(h([0]), []);
+      var h = histogram().bins([]);
       assert.deepEqual(h([0]), []);
     }
   }