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# Moment-generating function

> [Raised cosine][cosine-distribution] distribution [moment-generating function][mgf].

<section class="intro">

The [moment-generating function][mgf] for a [raised cosine][cosine-distribution] random variable is

<!-- <equation class="equation" label="eq:cosine_mgf" align="center" raw="M_X(t) := \mathbb{E}\!\left[e^{tX}\right] = \frac{ \pi^{2} \sinh(st) }{ st(\pi^{2}+s^{2}t^{2}) } \,e^{\mu t}" alt="Moment-generating function for a raised cosine distribution."> -->

<div class="equation" align="center" data-raw-text="M_X(t) := \mathbb{E}\!\left[e^{tX}\right] = \frac{ \pi^{2} \sinh(st) }{ st(\pi^{2}+s^{2}t^{2}) } \,e^{\mu t}" data-equation="eq:cosine_mgf">
    <img src="https://cdn.rawgit.com/stdlib-js/stdlib/7e0a95722efd9c771b129597380c63dc6715508b/lib/node_modules/@stdlib/stats/base/dists/cosine/mgf/docs/img/equation_cosine_mgf.svg" alt="Moment-generating function for a raised cosine distribution.">
    <br>
</div>

<!-- </equation> -->

where `μ` is the location parameter and `s > 0` is the scale parameter.

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var mgf = require( '@stdlib/stats/base/dists/cosine/mgf' );
```

#### mgf( t, mu, s )

Evaluates the [moment-generating function][mgf] (MGF) for a [raised cosine][cosine-distribution] distribution with parameters `mu` (location parameter) and `s` (scale parameter).

```javascript
var y = mgf( 2.0, 0.0, 3.0 );
// returns ~7.234

y = mgf( 0.5, 0.0, 1.0 );
// returns ~1.016

y = mgf( -1.0, 4.0, 2.0 );
// returns ~0.024
```

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

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

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

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

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

```javascript
var y = mgf( 0.5, 0.0, -1.0 );
// returns NaN

y = mgf( 0.5, 0.0, 0.0 );
// returns NaN
```

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

Returns a function for evaluating the [moment-generating function][mgf] of a [raised cosine][cosine-distribution] distribution with parameters `mu` (location parameter) and `s` (scale parameter).

```javascript
var mymgf = mgf.factory( 10.0, 2.0 );

var y = mymgf( 0.1 );
// returns ~2.725
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

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

```javascript
var randu = require( '@stdlib/random/base/randu' );
var mgf = require( '@stdlib/stats/base/dists/cosine/mgf' );

var mu;
var s;
var t;
var y;
var i;

for ( i = 0; i < 10; i++ ) {
    t = randu() * 10.0;
    mu = randu() * 10.0;
    s = randu() * 10.0;
    y = mgf( t, mu, s );
    console.log( 't: %d, µ: %d, s: %d, M_X(t;µ,s): %d', t.toFixed( 4 ), mu.toFixed( 4 ), s.toFixed( 4 ), y.toFixed( 4 ) );
}
```

</section>

<!-- /.examples -->

<section class="links">

[cosine-distribution]: https://en.wikipedia.org/wiki/Raised_cosine_distribution

[mgf]: https://en.wikipedia.org/wiki/Moment-generating_function

</section>

<!-- /.links -->
