algorithm: average/mean (#30)

Author: orangegrove1955

Maths/calculateMean.ts

@@ -0,0 +1,21 @@
+/**
+ * @function calculateMean
+ * @description This script will find the mean value of a array of numbers.
+ * @param {number[]} numbers - Array of numeric values
+ * @return {number} - mean of input numbers
+ * @see [Mean](https://en.wikipedia.org/wiki/Mean)
+ * @example calculateMean([1, 2, 4, 5]) = 3
+ * @example calculateMean([10, 40, 100, 20]) = 42.5
+ */
+
+export const calculateMean = (numbers: number[]): number => {
+  if (numbers.length < 1) {
+    throw new TypeError("Invalid Input");
+  }
+
+  // This loop sums all values in the 'numbers' array using an array reducer
+  const sum = numbers.reduce((sum, current) => sum + current, 0);
+
+  // Divide sum by the length of the 'numbers' array.
+  return sum / numbers.length;
+};

Maths/test/calculateMean.test.ts

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+import { calculateMean } from "../calculateMean";
+
+describe("Tests for AverageMean", () => {
+  it("should be a function", () => {
+    expect(typeof calculateMean).toEqual("function");
+  });
+
+  it("should throw error for invalid input", () => {
+    expect(() => calculateMean([])).toThrow();
+  });
+
+  it("should return the mean of an array of consecutive numbers", () => {
+    const meanFunction = calculateMean([1, 2, 3, 4]);
+    expect(meanFunction).toBe(2.5);
+  });
+
+  it("should return the mean of an array of numbers", () => {
+    const meanFunction = calculateMean([10, 40, 100, 20]);
+    expect(meanFunction).toBe(42.5);
+  });
+
+  it("should return the mean of an array of decimal numbers", () => {
+    const meanFunction = calculateMean([1.3, 12.67, 99.14, 20]);
+    expect(meanFunction).toBe(33.2775);
+  });
+
+  it("should return the mean of an array of numbers, including negatives", () => {
+    const meanFunction = calculateMean([10, -40, 100, -20]);
+    expect(meanFunction).toBe(12.5);
+  });
+});