feat: add xyMassCenter

closes: #238

src/__tests__/__snapshots__/index.test.ts.snap

@@ -87,6 +87,7 @@ exports[`test existence of exported functions 1`] = `
   "xyIntegral",
   "xyIntegration",
   "xyJoinX",
+  "xyMassCenter",
   "xyMassCenterVector",
   "xyMaxClosestYPoint",
   "xyMaximaY",

src/x/xMeanWeighted.ts

@@ -6,6 +6,7 @@ import { xGetFromToIndex, XGetFromToIndexOptions } from './xGetFromToIndex';
 /**
  * Computes the weighted mean value of an array of values.
  *
+ * @deprecated please use xyMassCenter
  * @param array - array of numbers
  * @param weights - array of weights
  * @param options - options

src/xy/__tests__/xyMassCenter.test.ts

@@ -0,0 +1,42 @@
+import { expect, test } from 'vitest';
+
+import { xyMassCenter } from '../xyMassCenter';
+
+test('xyMassCenter', () => {
+  const typedArray = Uint16Array.from([1, 2, 3, 4, 5]);
+
+  expect(xyMassCenter({ x: [0], y: [1] })).toBe(0);
+  expect(xyMassCenter({ x: [1], y: [1] })).toBe(1);
+  expect(xyMassCenter({ x: [1, 2], y: [1, 1] })).toBe(1.5);
+  expect(xyMassCenter({ x: [1, 2, 3], y: [1, 1, 1] })).toBe(2);
+  expect(xyMassCenter({ x: [3, 2, 1], y: [1, 1, 1] })).toBe(2);
+  expect(xyMassCenter({ x: typedArray, y: [1, 1, 1, 1, 1] })).toBe(3);
+  expect(xyMassCenter({ x: [1, 2, 3], y: [1, 1, 1] }, { fromIndex: 1 })).toBe(
+    2.5,
+  );
+  expect(xyMassCenter({ x: [3, 2, 1], y: [1, 1, 1] }, { fromIndex: 1 })).toBe(
+    1.5,
+  );
+  expect(xyMassCenter({ x: [1, 2, 3], y: [1, 1, 1] }, { toIndex: 1 })).toBe(
+    1.5,
+  );
+  expect(xyMassCenter({ x: [3, 2, 1], y: [1, 1, 1] }, { toIndex: 1 })).toBe(
+    2.5,
+  );
+  expect(
+    xyMassCenter({ x: [1, 2, 3], y: [1, 1, 1] }, { fromIndex: 1, toIndex: 1 }),
+  ).toBe(2);
+  expect(
+    xyMassCenter({ x: [1, 2, 3], y: [1, 1, 1] }, { fromIndex: 1, toIndex: 10 }),
+  ).toBe(2.5);
+  expect(
+    xyMassCenter({ x: [3, 2, 1], y: [1, 1, 1] }, { fromIndex: 1, toIndex: 1 }),
+  ).toBe(2);
+  expect(() => xyMassCenter({ x: [], y: [] })).toThrow(
+    'data.x must have a length of at least',
+  );
+  expect(() => xyMassCenter({ x: [1], y: [] })).toThrow(
+    'the x and y arrays must have the same',
+  );
+  expect(xyMassCenter({ x: [1, 2, 3], y: [0, 0, 0] })).toBe(0);
+});

src/xy/index.ts

@@ -17,6 +17,7 @@ export * from './xyGrowingX';
 export * from './xyIntegral';
 export * from './xyIntegration';
 export * from './xyJoinX';
+export * from './xyMassCenter';
 export * from './xyMassCenterVector';
 export * from './xyMaxClosestYPoint';
 export * from './xyMaximaY';

src/xy/xyMassCenter.ts

@@ -0,0 +1,29 @@
+import { DataXY } from 'cheminfo-types';
+
+import { xGetFromToIndex, XGetFromToIndexOptions } from '../x/xGetFromToIndex';
+
+import { xyCheck } from '.';
+
+/**
+ * Computes the weighted mean value of an array of values.
+ *
+ * @param data - array of DataXY
+ * @param options - options
+ */
+export function xyMassCenter(
+  data: DataXY,
+  options: XGetFromToIndexOptions = {},
+): number {
+  xyCheck(data, { minLength: 1 });
+  const { x, y } = data;
+  const { fromIndex, toIndex } = xGetFromToIndex(x, options);
+
+  let sumWeights = 0;
+  let sumValue = 0;
+  for (let i = fromIndex; i <= toIndex; i++) {
+    sumValue += x[i] * y[i];
+    sumWeights += y[i];
+  }
+
+  return sumValue / sumWeights;
+}