Index: node_modules/d3-polygon/src/centroid.js
===================================================================
--- node_modules/d3-polygon/src/centroid.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-polygon/src/centroid.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,20 @@
+export default function(polygon) {
+  var i = -1,
+      n = polygon.length,
+      x = 0,
+      y = 0,
+      a,
+      b = polygon[n - 1],
+      c,
+      k = 0;
+
+  while (++i < n) {
+    a = b;
+    b = polygon[i];
+    k += c = a[0] * b[1] - b[0] * a[1];
+    x += (a[0] + b[0]) * c;
+    y += (a[1] + b[1]) * c;
+  }
+
+  return k *= 3, [x / k, y / k];
+}