diff -r efd9c589177a -r c0b4a8b5a012 toolkit/javascript/d3/src/core/mean.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/javascript/d3/src/core/mean.js	Thu Apr 10 14:20:23 2014 +0200
@@ -0,0 +1,13 @@
+d3.mean = function(array, f) {
+  var n = array.length,
+      a,
+      m = 0,
+      i = -1,
+      j = 0;
+  if (arguments.length === 1) {
+    while (++i < n) if (d3_number(a = array[i])) m += (a - m) / ++j;
+  } else {
+    while (++i < n) if (d3_number(a = f.call(array, array[i], i))) m += (a - m) / ++j;
+  }
+  return j ? m : undefined;
+};