From 258b35d1a2f1fe7407098a95e31004557ea4577c Mon Sep 17 00:00:00 2001
From: Vasco Asturiano <vasturiano@medallia.com>
Date: Fri, 23 Jun 2017 00:35:55 -0700
Subject: [PATCH] Correct weighted average in barnes-hut coordinates

---
 src/manyBody.js | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/manyBody.js b/src/manyBody.js
index d9887c9..8dbf5c8 100644
--- a/src/manyBody.js
+++ b/src/manyBody.js
@@ -26,17 +26,17 @@ export default function() {
   }
 
   function accumulate(quad) {
-    var strength = 0, q, c, x, y, i;
+    var strength = 0, q, c, sumC = 0, x, y, i;
 
     // For internal nodes, accumulate forces from child quadrants.
     if (quad.length) {
       for (x = y = i = 0; i < 4; ++i) {
-        if ((q = quad[i]) && (c = q.value)) {
-          strength += c, x += c * q.x, y += c * q.y;
+        if ((q = quad[i]) && (c = Math.abs(q.value))) {
+          strength += q.value, sumC += c, x += c * q.x, y += c * q.y;
         }
       }
-      quad.x = x / strength;
-      quad.y = y / strength;
+      quad.x = x / sumC;
+      quad.y = y / sumC;
     }
 
     // For leaf nodes, accumulate forces from coincident quadrants.