diff -r efd9c589177a -r c0b4a8b5a012 toolkit/javascript/d3/src/layout/cluster.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/javascript/d3/src/layout/cluster.js	Thu Apr 10 14:20:23 2014 +0200
@@ -0,0 +1,78 @@
+// Implements a hierarchical layout using the cluster (or dendogram) algorithm.
+d3.layout.cluster = function() {
+  var hierarchy = d3.layout.hierarchy().sort(null).value(null),
+      separation = d3_layout_treeSeparation,
+      size = [1, 1]; // width, height
+
+  function cluster(d, i) {
+    var nodes = hierarchy.call(this, d, i),
+        root = nodes[0],
+        previousNode,
+        x = 0,
+        kx,
+        ky;
+
+    // First walk, computing the initial x & y values.
+    d3_layout_treeVisitAfter(root, function(node) {
+      var children = node.children;
+      if (children && children.length) {
+        node.x = d3_layout_clusterX(children);
+        node.y = d3_layout_clusterY(children);
+      } else {
+        node.x = previousNode ? x += separation(node, previousNode) : 0;
+        node.y = 0;
+        previousNode = node;
+      }
+    });
+
+    // Compute the left-most, right-most, and depth-most nodes for extents.
+    var left = d3_layout_clusterLeft(root),
+        right = d3_layout_clusterRight(root),
+        x0 = left.x - separation(left, right) / 2,
+        x1 = right.x + separation(right, left) / 2;
+
+    // Second walk, normalizing x & y to the desired size.
+    d3_layout_treeVisitAfter(root, function(node) {
+      node.x = (node.x - x0) / (x1 - x0) * size[0];
+      node.y = (1 - node.y / root.y) * size[1];
+    });
+
+    return nodes;
+  }
+
+  cluster.separation = function(x) {
+    if (!arguments.length) return separation;
+    separation = x;
+    return cluster;
+  };
+
+  cluster.size = function(x) {
+    if (!arguments.length) return size;
+    size = x;
+    return cluster;
+  };
+
+  return d3_layout_hierarchyRebind(cluster, hierarchy);
+};
+
+function d3_layout_clusterY(children) {
+  return 1 + d3.max(children, function(child) {
+    return child.y;
+  });
+}
+
+function d3_layout_clusterX(children) {
+  return children.reduce(function(x, child) {
+    return x + child.x;
+  }, 0) / children.length;
+}
+
+function d3_layout_clusterLeft(node) {
+  var children = node.children;
+  return children && children.length ? d3_layout_clusterLeft(children[0]) : node;
+}
+
+function d3_layout_clusterRight(node) {
+  var children = node.children, n;
+  return children && (n = children.length) ? d3_layout_clusterRight(children[n - 1]) : node;
+}