# @stdlib/stats-base-dists-negative-binomial-mode

0.2.1 • Public • Published

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# Mode

Negative binomial distribution mode.

The mode for a negative-binomial random variable is

where `r` is the number of successes until experiment is stopped and `p` is the success probability in each trial. The random variable `X` denotes the number of failures until the `r` success is reached.

## Installation

`npm install @stdlib/stats-base-dists-negative-binomial-mode`

## Usage

`var mode = require( '@stdlib/stats-base-dists-negative-binomial-mode' );`

#### mode( r, p )

Returns the mode of a negative binomial distribution with parameters `r` (number of successes until experiment is stopped) and `p` (success probability).

```var v = mode( 100, 0.2 );
// returns 396

v = mode( 50, 0.5 );
// returns 49```

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

```var v = mode( NaN, 0.5 );
// returns NaN

v = mode( 20, NaN );
// returns NaN```

If provided a `r` which is not a positive number, the function returns `NaN`.

```var v = mode( -2.0, 0.5 );
// returns NaN```

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

```var v = mode( 20, -1.0 );
// returns NaN

v = mode( 20, 1.5 );
// returns NaN```

## Examples

```var randu = require( '@stdlib/random-base-randu' );
var mode = require( '@stdlib/stats-base-dists-negative-binomial-mode' );

var v;
var i;
var r;
var p;

for ( i = 0; i < 10; i++ ) {
r = randu() * 100;
p = randu();
v = mode( r, p );
console.log( 'r: %d, p: %d, mode(X;r,p): %d', r, p.toFixed( 4 ), v.toFixed( 4 ) );
}```

## 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-negative-binomial-mode`

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