Fix d3.mean: coerce strings to numbers.

Fixes #2067.

d3.js

@@ -93,9 +93,9 @@
   d3.mean = function(array, f) {
     var s = 0, n = array.length, a, i = -1, j = n;
     if (arguments.length === 1) {
-      while (++i < n) if (d3_number(a = array[i])) s += a; else --j;
+      while (++i < n) if (d3_number(a = array[i])) s += +a; else --j;
     } else {
-      while (++i < n) if (d3_number(a = f.call(array, array[i], i))) s += a; else --j;
+      while (++i < n) if (d3_number(a = f.call(array, array[i], i))) s += +a; else --j;
     }
     return j ? s / j : undefined;
   };

src/arrays/mean.js

@@ -7,9 +7,9 @@ d3.mean = function(array, f) {
       i = -1,
       j = n;
   if (arguments.length === 1) {
-    while (++i < n) if (d3_number(a = array[i])) s += a; else --j;
+    while (++i < n) if (d3_number(a = array[i])) s += +a; else --j;
   } else {
-    while (++i < n) if (d3_number(a = f.call(array, array[i], i))) s += a; else --j;
+    while (++i < n) if (d3_number(a = f.call(array, array[i], i))) s += +a; else --j;
   }
   return j ? s / j : undefined;
 };

test/arrays/mean-test.js

@@ -28,6 +28,12 @@ suite.addBatch({
     "applies the optional accessor function": function(mean) {
       assert.equal(mean([[1, 2, 3, 4, 5], [2, 4, 6, 8, 10]], function(d) { return mean(d); }), 4.5);
       assert.equal(mean([1, 2, 3, 4, 5], function(d, i) { return i; }), 2);
+    },
+    "coerces strings to numbers": function(mean) {
+      assert.equal(mean(["1"]), 1);
+      assert.equal(mean(["5", "1", "2", "3", "4"]), 3);
+      assert.equal(mean(["20", "3"]), 11.5);
+      assert.equal(mean(["3", "20"]), 11.5);
     }
   }
 });