18 lines
646 B
Markdown
18 lines
646 B
Markdown
### Standard deviation
|
|
|
|
Use `Array.reduce()` to calculate the mean of the values, the variance of the values, and the sum of the variance
|
|
of the values to determine the standard deviation of an array of numbers.
|
|
|
|
NOTE: This is **population standard deviation**. Use `/ (arr.length - 1)` at the end to
|
|
calculate **sample standard deviation**.
|
|
|
|
```js
|
|
const standardDeviation = arr =>
|
|
Math.sqrt(
|
|
arr.reduce((acc, val) => acc.concat(Math.pow(val - arr.reduce((acc, val) => acc + val, 0) / arr.length, 2)), [])
|
|
.reduce((acc, val) => acc + val, 0)
|
|
/ arr.length
|
|
);
|
|
// standardDeviation([10,2,38,23,38,23,21]) -> 12.298996142875
|
|
```
|