npm package: @stdlib/stats-base-dists-levy-stdev
Description: Lévy distribution standard deviation.
Author: The Stdlib Authors
Latest version: 0.3.1

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# Standard Deviation

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> [Lévy][levy-distribution] distribution [standard deviation][standard-deviation].

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<section class="intro">

The [standard deviation][standard-deviation] for a [Lévy][levy-distribution] random variable with location `μ` and scale `c > 0` is

<!-- <equation class="equation" label="eq:levy_stdev" align="center" raw="\sigma = \infty" alt="Standard deviation for a Lévy distribution."> -->

<div class="equation" align="center" data-raw-text="\sigma = \infty" data-equation="eq:levy_stdev">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@51534079fef45e990850102147e8945fb023d1d0/lib/node_modules/@stdlib/stats/base/dists/levy/stdev/docs/img/equation_levy_stdev.svg" alt="Standard deviation for a Lévy distribution.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/stats-base-dists-levy-stdev
```

</section>

<section class="usage">

## Usage

```javascript
var stdev = require( '@stdlib/stats-base-dists-levy-stdev' );
```

#### stdev( mu, c )

Returns the [standard deviation][standard-deviation] for a [Lévy][levy-distribution] distribution with location parameter `mu` and scale parameter `c`.

```javascript
var y = stdev( 2.0, 1.0 );
// returns Infinity

y = stdev( 0.0, 1.0 );
// returns Infinity

y = stdev( -1.0, 4.0 );
// returns Infinity
```

If provided `NaN` as any argument, the function returns `NaN`.

```javascript
var y = stdev( NaN, 1.0 );
// returns NaN

y = stdev( 0.0, NaN );
// returns NaN
```

If provided `c <= 0`, the function returns `NaN`.

```javascript
var y = stdev( 0.0, 0.0 );
// returns NaN

y = stdev( 0.0, -1.0 );
// returns NaN
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random-base-randu' );
var stdev = require( '@stdlib/stats-base-dists-levy-stdev' );

var mu;
var c;
var y;
var i;

for ( i = 0; i < 10; i++ ) {
    mu = ( randu()*10.0 ) - 5.0;
    c = randu() * 20.0;
    y = stdev( mu, c );
    console.log( 'µ: %d, c: %d, SD(X;µ,c): %d', mu.toFixed( 4 ), c.toFixed( 4 ), y.toFixed( 4 ) );
}
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/stats/base/dists/levy/stdev.h"
```

#### stdlib_base_dists_levy_stdev( mu, c )

Returns the [standard deviation][standard-deviation] for a [Lévy][levy-distribution] distribution with location parameter `mu` and scale parameter `c`.

```c
double out = stdlib_base_dists_levy_stdev( 0.0, 1.0 );
// returns Infinity
```

The function accepts the following arguments:

-   **mu**: `[in] double` location parameter.
-   **c**: `[in] double` scale parameter.

```c
double stdlib_base_dists_levy_stdev( const double mu, const double c );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/stats/base/dists/levy/stdev.h"
#include <stdlib.h>
#include <stdio.h>

static double random_uniform( const double min, const double max ) {
    double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
    return min + ( v*(max-min) );
}

int main( void ) {
    double mu;
    double c;
    double y;
    int i;

    for ( i = 0; i < 25; i++ ) {
        mu = random_uniform( -5.0, 5.0 );
        c = random_uniform( 0.0, 20.0 );
        y = stdlib_base_dists_levy_stdev( mu, c );
        printf( "µ: %lf, c: %lf, SD(X;µ,c): %lf\n", mu, c, y );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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</section>

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</section>

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* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/stats-base-dists-levy-stdev/main/LICENSE

[levy-distribution]: https://en.wikipedia.org/wiki/L%C3%A9vy_distribution

[standard-deviation]: https://en.wikipedia.org/wiki/Standard_deviation

</section>

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