# @stdlib/stats-base-dists-logistic-quantile

0.2.1 • Public • Published

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# Quantile Function

Logistic distribution quantile function.

The quantile function for a logistic random variable is

for `0 <= p < 1`, where `µ` is the location parameter and `s > 0` is the scale parameter.

## Installation

`npm install @stdlib/stats-base-dists-logistic-quantile`

## Usage

`var quantile = require( '@stdlib/stats-base-dists-logistic-quantile' );`

#### quantile( p, mu, s )

Evaluates the quantile function for a logistic distribution with parameters `mu` (location parameter) and `s` (scale parameter).

```var y = quantile( 0.5, 0.0, 1.0 );
// returns 0.0

y = quantile( 0.2, 4.0, 2.0 );
// returns ~1.227```

If provided a probability `p` outside the interval `[0,1]`, the function returns `NaN`.

```var y = quantile( 1.9, 0.0, 1.0 );
// returns NaN

y = quantile( -0.1, 0.0, 1.0 );
// returns NaN```

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

```var y = quantile( NaN, 0.0, 1.0 );
// returns NaN

y = quantile( 0.0, NaN, 1.0 );
// returns NaN

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

If provided `s < 0`, the function returns `NaN`.

```var y = quantile( 0.4, 0.0, -1.0 );
// returns NaN```

If provided `s = 0`, the function evaluates the quantile function of a degenerate distribution centered at `mu`.

```var y = quantile( 0.3, 8.0, 0.0 );
// returns 8.0

y = quantile( 0.9, 8.0, 0.0 );
// returns 8.0```

#### quantile.factory( mu, s )

Returns a function for evaluating the quantile function of a logistic distribution with parameters `mu` and `s`.

```var myQuantile = quantile.factory( 10.0, 2.0 );

var y = myQuantile( 0.2 );
// returns ~7.227

y = myQuantile( 0.8 );
// returns ~12.773```

## Examples

```var randu = require( '@stdlib/random-base-randu' );
var quantile = require( '@stdlib/stats-base-dists-logistic-quantile' );

var mu;
var s;
var p;
var y;
var i;

for ( i = 0; i < 10; i++ ) {
p = randu();
mu = randu() * 10.0;
s = randu() * 10.0;
y = quantile( p, mu, s );
console.log( 'p: %d, µ: %d, s: %d, Q(p;µ,s): %d', p, mu, s, y );
}```

## Notice

This package is part of 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, see the main project repository.

## Package Sidebar

### Install

`npm i @stdlib/stats-base-dists-logistic-quantile`

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