Index: node_modules/d3-geo/src/path/centroid.js
===================================================================
--- node_modules/d3-geo/src/path/centroid.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-geo/src/path/centroid.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,100 @@
+import {sqrt} from "../math.js";
+
+// TODO Enforce positive area for exterior, negative area for interior?
+
+var X0 = 0,
+    Y0 = 0,
+    Z0 = 0,
+    X1 = 0,
+    Y1 = 0,
+    Z1 = 0,
+    X2 = 0,
+    Y2 = 0,
+    Z2 = 0,
+    x00,
+    y00,
+    x0,
+    y0;
+
+var centroidStream = {
+  point: centroidPoint,
+  lineStart: centroidLineStart,
+  lineEnd: centroidLineEnd,
+  polygonStart: function() {
+    centroidStream.lineStart = centroidRingStart;
+    centroidStream.lineEnd = centroidRingEnd;
+  },
+  polygonEnd: function() {
+    centroidStream.point = centroidPoint;
+    centroidStream.lineStart = centroidLineStart;
+    centroidStream.lineEnd = centroidLineEnd;
+  },
+  result: function() {
+    var centroid = Z2 ? [X2 / Z2, Y2 / Z2]
+        : Z1 ? [X1 / Z1, Y1 / Z1]
+        : Z0 ? [X0 / Z0, Y0 / Z0]
+        : [NaN, NaN];
+    X0 = Y0 = Z0 =
+    X1 = Y1 = Z1 =
+    X2 = Y2 = Z2 = 0;
+    return centroid;
+  }
+};
+
+function centroidPoint(x, y) {
+  X0 += x;
+  Y0 += y;
+  ++Z0;
+}
+
+function centroidLineStart() {
+  centroidStream.point = centroidPointFirstLine;
+}
+
+function centroidPointFirstLine(x, y) {
+  centroidStream.point = centroidPointLine;
+  centroidPoint(x0 = x, y0 = y);
+}
+
+function centroidPointLine(x, y) {
+  var dx = x - x0, dy = y - y0, z = sqrt(dx * dx + dy * dy);
+  X1 += z * (x0 + x) / 2;
+  Y1 += z * (y0 + y) / 2;
+  Z1 += z;
+  centroidPoint(x0 = x, y0 = y);
+}
+
+function centroidLineEnd() {
+  centroidStream.point = centroidPoint;
+}
+
+function centroidRingStart() {
+  centroidStream.point = centroidPointFirstRing;
+}
+
+function centroidRingEnd() {
+  centroidPointRing(x00, y00);
+}
+
+function centroidPointFirstRing(x, y) {
+  centroidStream.point = centroidPointRing;
+  centroidPoint(x00 = x0 = x, y00 = y0 = y);
+}
+
+function centroidPointRing(x, y) {
+  var dx = x - x0,
+      dy = y - y0,
+      z = sqrt(dx * dx + dy * dy);
+
+  X1 += z * (x0 + x) / 2;
+  Y1 += z * (y0 + y) / 2;
+  Z1 += z;
+
+  z = y0 * x - x0 * y;
+  X2 += z * (x0 + x);
+  Y2 += z * (y0 + y);
+  Z2 += z * 3;
+  centroidPoint(x0 = x, y0 = y);
+}
+
+export default centroidStream;