diff -r efd9c589177a -r c0b4a8b5a012 toolkit/javascript/d3/examples/stream/stream_layers.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/javascript/d3/examples/stream/stream_layers.js	Thu Apr 10 14:20:23 2014 +0200
@@ -0,0 +1,33 @@
+/* Inspired by Lee Byron's test data generator. */
+function stream_layers(n, m, o) {
+  if (arguments.length < 3) o = 0;
+  function bump(a) {
+    var x = 1 / (.1 + Math.random()),
+        y = 2 * Math.random() - .5,
+        z = 10 / (.1 + Math.random());
+    for (var i = 0; i < m; i++) {
+      var w = (i / m - y) * z;
+      a[i] += x * Math.exp(-w * w);
+    }
+  }
+  return d3.range(n).map(function() {
+      var a = [], i;
+      for (i = 0; i < m; i++) a[i] = o + o * Math.random();
+      for (i = 0; i < 5; i++) bump(a);
+      return a.map(stream_index);
+    });
+}
+
+/* Another layer generator using gamma distributions. */
+function stream_waves(n, m) {
+  return d3.range(n).map(function(i) {
+    return d3.range(m).map(function(j) {
+        var x = 20 * j / m - i / 3;
+        return 2 * x * Math.exp(-.5 * x);
+      }).map(stream_index);
+    });
+}
+
+function stream_index(d, i) {
+  return {x: i, y: Math.max(0, d)};
+}