feat: Added Standard Deviation algorithm for Math #1680

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	/*
	* Returns the standard deviation given an array of integers
	* @param number[] nums array of integers
	* @return number 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 (typeof nums[i] != 'number') {
	throw new TypeError('Number 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 }

36 changes: 36 additions & 0 deletions Maths/test/StandardDeviation.test.js

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	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()
	})

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