40% faster turf-area (#2520)

* Merge pull request #1387 from pirxpilot:area

* Fix optimized ringArea

* Regen nearest-neighbor-analysis

* Add rest of out tests

* update turf-area benchmark

Author: AminoffZ

packages/turf-area/bench.js

@@ -17,7 +17,7 @@ const fixtures = fs.readdirSync(directory).map((filename) => {
 /**
  * Benmark Results
  *
- * polygon x 3,240,248 ops/sec ±0.91% (90 runs sampled)
+ * polygon x 8,510,024 ops/sec ±0.28% (96 runs sampled)
  */
 
 // Define benchmark

packages/turf-area/index.ts

@@ -67,6 +67,24 @@ function polygonArea(coords: any) {
   return total;
 }
 
+/**
+ * @private
+ * A constant factor used to compute the area of a polygon.
+ * It's derived from the square of the Earth's radius divided by 2.
+ *
+ * @type {number}
+ */
+const FACTOR = (earthRadius * earthRadius) / 2;
+
+/**
+ * @private
+ * A constant used for converting degrees to radians.
+ * Represents the ratio of PI to 180.
+ *
+ * @type {number}
+ */
+const PI_OVER_180 = Math.PI / 180;
+
 /**
  * @private
  * Calculate the approximate area of the polygon were it projected onto the earth.
@@ -80,46 +98,27 @@ function polygonArea(coords: any) {
  * @param {Array<Array<number>>} coords Ring Coordinates
  * @returns {number} The approximate signed geodesic area of the polygon in square meters.
  */
-function ringArea(coords: number[][]) {
-  let p1;
-  let p2;
-  let p3;
-  let lowerIndex;
-  let middleIndex;
-  let upperIndex;
-  let i;
-  let total = 0;
+function ringArea(coords: number[][]): number {
   const coordsLength = coords.length;
 
-  if (coordsLength > 2) {
-    for (i = 0; i < coordsLength; i++) {
-      if (i === coordsLength - 2) {
-        // i = N-2
-        lowerIndex = coordsLength - 2;
-        middleIndex = coordsLength - 1;
-        upperIndex = 0;
-      } else if (i === coordsLength - 1) {
-        // i = N-1
-        lowerIndex = coordsLength - 1;
-        middleIndex = 0;
-        upperIndex = 1;
-      } else {
-        // i = 0 to N-3
-        lowerIndex = i;
-        middleIndex = i + 1;
-        upperIndex = i + 2;
-      }
-      p1 = coords[lowerIndex];
-      p2 = coords[middleIndex];
-      p3 = coords[upperIndex];
-      total += (rad(p3[0]) - rad(p1[0])) * Math.sin(rad(p2[1]));
-    }
+  if (coordsLength <= 2) return 0;
+  let total = 0;
 
-    total = (total * earthRadius * earthRadius) / 2;
+  let i = 0;
+  while (i < coordsLength) {
+    const lower = coords[i];
+    const middle = coords[i + 1 === coordsLength ? 0 : i + 1];
+    const upper =
+      coords[i + 2 >= coordsLength ? (i + 2) % coordsLength : i + 2];
+
+    const lowerX = lower[0] * PI_OVER_180;
+    const middleY = middle[1] * PI_OVER_180;
+    const upperX = upper[0] * PI_OVER_180;
+
+    total += (upperX - lowerX) * Math.sin(middleY);
+
+    i++;
   }
-  return total;
-}
 
-function rad(num: number) {
-  return (num * Math.PI) / 180;
+  return total * FACTOR;
 }

packages/turf-nearest-neighbor-analysis/test/out/random-large-study-area.json

@@ -1211,10 +1211,10 @@
           "units": "kilometers",
           "arealUnits": "kilometers²",
           "observedMeanDistance": 1.6516270145942438,
-          "expectedMeanDistance": 25.461470908340697,
-          "nearestNeighborIndex": 0.06486769835646855,
+          "expectedMeanDistance": 25.46147090834068,
+          "nearestNeighborIndex": 0.0648676983564686,
           "numberOfPoints": 150,
-          "zScore": -21.910362919163752
+          "zScore": -21.91036291916375
         }
       },
       "geometry": {

packages/turf-nearest-neighbor-analysis/test/out/random-outlier.json

@@ -1220,10 +1220,10 @@
           "units": "kilometers",
           "arealUnits": "kilometers²",
           "observedMeanDistance": 7.363991103875287,
-          "expectedMeanDistance": 25.37702057977424,
-          "nearestNeighborIndex": 0.29018343901823007,
+          "expectedMeanDistance": 25.377020579774225,
+          "nearestNeighborIndex": 0.29018343901823024,
           "numberOfPoints": 151,
-          "zScore": -16.68650889595032
+          "zScore": -16.686508895950315
         }
       },
       "geometry": {

packages/turf-nearest-neighbor-analysis/test/out/random.json

@@ -1217,10 +1217,10 @@
           "units": "kilometers",
           "arealUnits": "kilometers²",
           "observedMeanDistance": 1.6516270145942438,
-          "expectedMeanDistance": 1.5869473002517003,
-          "nearestNeighborIndex": 1.0407573171032742,
+          "expectedMeanDistance": 1.5869473002516816,
+          "nearestNeighborIndex": 1.0407573171032865,
           "numberOfPoints": 150,
-          "zScore": 0.9549532272328554
+          "zScore": 0.9549532272331418
         }
       },
       "geometry": {

packages/turf-nearest-neighbor-analysis/test/out/squares.json

@@ -1473,10 +1473,10 @@
           "units": "kilometers",
           "arealUnits": "kilometers²",
           "observedMeanDistance": 4.986280150858801,
-          "expectedMeanDistance": 2.496567669388766,
-          "nearestNeighborIndex": 1.997254154973332,
+          "expectedMeanDistance": 2.4965676693887655,
+          "nearestNeighborIndex": 1.9972541549733325,
           "numberOfPoints": 56,
-          "zScore": 14.27679589626176
+          "zScore": 14.276795896261763
         }
       },
       "geometry": {