feat: Added Standard Deviation algorithm for Math

Author: justclaner

Maths/StandardDeviation.js

@@ -0,0 +1,32 @@
+/*
+ * Returns the standard deviation given an array of integers
+ * @param  int[]   nums    array of integers
+ * @return int             standard deviation
+ * @see https://en.wikipedia.org/wiki/Standard_deviation
+ */
+function standardDeviation(nums) {
+  if (nums.length < 2) {
+    throw new Error('At least two numbers in input array are required!')
+  }
+  if (!Array.isArray(nums)) {
+    throw new TypeError('Array required!')
+  }
+
+  let sum = 0
+  for (let i = 0; i < nums.length; i++) {
+    if (!Number.isInteger(nums[i])) {
+      throw new TypeError('Integer type required in array input!')
+    }
+    sum += nums[i]
+  }
+  let avg = sum / nums.length
+  let deviationSquareSum = 0
+  for (let i = 0; i < nums.length; i++) {
+    let square = Math.pow(nums[i] - avg, 2)
+    deviationSquareSum += square
+  }
+
+  return Math.sqrt(deviationSquareSum / nums.length)
+}
+
+export { standardDeviation }

Maths/test/StandardDeviation.test.js

@@ -0,0 +1,36 @@
+import { standardDeviation } from '../StandardDeviation.js'
+
+test('Calculate STD of 3,5,6,10,23,12,19', () => {
+  expect(standardDeviation([3, 5, 6, 10, 23, 12, 19])).toBeCloseTo(
+    6.9164105353773
+  )
+})
+
+test('Calculate STD of -2,-5,1,12,23,-81,-23', () => {
+  expect(standardDeviation([-2, -5, 1, 12, 23, -81, -23])).toBeCloseTo(
+    31.598889156399
+  )
+})
+
+test('Calculate STD of 0,0,0', () => {
+  expect(standardDeviation([0, 0, 0])).toBeCloseTo(0)
+})
+
+test('Calculate STD of -7,7', () => {
+  expect(standardDeviation([-7, 7])).toBeCloseTo(7)
+})
+
+test('Throw error - array has less than two items', () => {
+  expect(() => standardDeviation([])).toThrow()
+  expect(() => standardDeviation([7])).toThrow()
+})
+
+test('Throw type error - not an array', () => {
+  expect(() => standardDeviation(2)).toThrow()
+  expect(() => standardDeviation('not an array')).toThrow()
+})
+
+test('Throw type error - not a number inside array', () => {
+  expect(() => standardDeviation([5, 'not a number', 2])).toThrow()
+  expect(() => standardDeviation([1, [2], 3])).toThrow()
+})