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JavaScript: Get the standard deviation of an array of numbers

JavaScript fundamental (ES6 Syntax): Exercise-225 with Solution

Write a JavaScript program to get the standard deviation of an array of numbers.

  • Use Array.prototype.reduce() to calculate the mean, variance and the sum of the variance of the values and determine the standard deviation.
  • Omit the second argument, usePopulation, to get the sample standard deviation or set it to true to get the population standard deviation.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const standardDeviation = (arr, usePopulation = false) => {
  const mean = arr.reduce((acc, val) => acc + val, 0) / arr.length;
  return Math.sqrt(
    arr.reduce((acc, val) => acc.concat((val - mean) ** 2), []).reduce((acc, val) => acc + val, 0) /
      (arr.length - (usePopulation ? 0 : 1))
  );
};

console.log(standardDeviation([10, 2, 38, 23, 38, 23, 21]));
console.log(standardDeviation([10, 2, 38, 23, 38, 23, 21], true));

Sample Output:

13.284434142114991
12.29899614287479

Flowchart:

flowchart: Get the standard deviation of an array of numbers.

Live Demo:

See the Pen javascript-basic-exercise-225-1 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found: 

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

Ref: https://bit.ly/3fFFgZv