74 lines
1.4 KiB
Markdown
74 lines
1.4 KiB
Markdown
---
|
|
title: Averages/Root mean square
|
|
id: 594da033de4190850b893874
|
|
challengeType: 5
|
|
forumTopicId: 302228
|
|
---
|
|
|
|
## Description
|
|
<section id='description'>
|
|
Compute the <a href="https://en.wikipedia.org/wiki/Root mean square" title="wp: Root mean square" target='_blank'>Root mean square</a> of the numbers 1 through 10 inclusive.
|
|
The <i>root mean square</i> is also known by its initials RMS (or rms), and as the <strong>quadratic mean</strong>.
|
|
The RMS is calculated as the mean of the squares of the numbers, square-rooted:
|
|
<big>$$x_{\mathrm{rms}} = \sqrt {{{x_1}^2 + {x_2}^2 + \cdots + {x_n}^2} \over n}. $$</big>
|
|
</section>
|
|
|
|
## Instructions
|
|
<section id='instructions'>
|
|
|
|
</section>
|
|
|
|
## Tests
|
|
<section id='tests'>
|
|
|
|
```yml
|
|
tests:
|
|
- text: <code>rms</code> should be a function.
|
|
testString: assert(typeof rms === 'function');
|
|
- text: <code>rms([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])</code> should equal <code>6.2048368229954285</code>.
|
|
testString: assert.equal(rms(arr1), answer1);
|
|
|
|
```
|
|
|
|
</section>
|
|
|
|
## Challenge Seed
|
|
<section id='challengeSeed'>
|
|
|
|
<div id='js-seed'>
|
|
|
|
```js
|
|
function rms(arr) {
|
|
|
|
}
|
|
```
|
|
|
|
</div>
|
|
|
|
|
|
### After Test
|
|
<div id='js-teardown'>
|
|
|
|
```js
|
|
const arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
|
|
const answer1 = 6.2048368229954285;
|
|
```
|
|
|
|
</div>
|
|
|
|
</section>
|
|
|
|
## Solution
|
|
<section id='solution'>
|
|
|
|
|
|
```js
|
|
function rms(arr) {
|
|
const sumOfSquares = arr.reduce((s, x) => s + x * x, 0);
|
|
return Math.sqrt(sumOfSquares / arr.length);
|
|
}
|
|
|
|
```
|
|
|
|
</section>
|