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