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# Inverse Gamma

> Inverse gamma distribution.

<section class="usage">

## Usage

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

#### invgamma

Inverse gamma distribution.

```javascript
var dist = invgamma;
// returns {...}
```

The namespace contains the following distribution functions:

<!-- <toc pattern="*+(cdf|pdf|mgf|quantile)*"> -->

<div class="namespace-toc">

-   <span class="signature">[`cdf( x, alpha, beta )`][@stdlib/stats/base/dists/invgamma/cdf]</span><span class="delimiter">: </span><span class="description">inverse Gamma distribution cumulative distribution function.</span>
-   <span class="signature">[`logpdf( x, alpha, beta )`][@stdlib/stats/base/dists/invgamma/logpdf]</span><span class="delimiter">: </span><span class="description">evaluate the natural logarithm of the probability density function (PDF) for an inverse gamma distribution.</span>
-   <span class="signature">[`pdf( x, alpha, beta )`][@stdlib/stats/base/dists/invgamma/pdf]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution probability density function (PDF).</span>
-   <span class="signature">[`quantile( p, alpha, beta )`][@stdlib/stats/base/dists/invgamma/quantile]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution quantile function.</span>

</div>

<!-- </toc> -->

The namespace contains the following functions for calculating distribution properties:

<!-- <toc pattern="*+(entropy|kurtosis|mean|median|mode|skewness|stdev|variance)*"> -->

<div class="namespace-toc">

-   <span class="signature">[`entropy( alpha, beta )`][@stdlib/stats/base/dists/invgamma/entropy]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution differential entropy.</span>
-   <span class="signature">[`kurtosis( alpha, beta )`][@stdlib/stats/base/dists/invgamma/kurtosis]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution excess kurtosis.</span>
-   <span class="signature">[`mean( alpha, beta )`][@stdlib/stats/base/dists/invgamma/mean]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution expected value.</span>
-   <span class="signature">[`mode( alpha, beta )`][@stdlib/stats/base/dists/invgamma/mode]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution mode.</span>
-   <span class="signature">[`skewness( alpha, beta )`][@stdlib/stats/base/dists/invgamma/skewness]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution skewness.</span>
-   <span class="signature">[`stdev( alpha, beta )`][@stdlib/stats/base/dists/invgamma/stdev]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution standard deviation.</span>
-   <span class="signature">[`variance( alpha, beta )`][@stdlib/stats/base/dists/invgamma/variance]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution variance.</span>

</div>

<!-- </toc> -->

The namespace contains a constructor function for creating a [inverse gamma][invgamma-distribution] distribution object.

<!-- <toc pattern="*ctor*"> -->

<div class="namespace-toc">

-   <span class="signature">[`InvGamma( [alpha, beta] )`][@stdlib/stats/base/dists/invgamma/ctor]</span><span class="delimiter">: </span><span class="description">inverse gamma distribution constructor.</span>

</div>

<!-- </toc> -->

```javascript
var InvGamma = require( '@stdlib/stats/base/dists/invgamma' ).InvGamma;

var dist = new InvGamma( 2.0, 4.0 );

var y = dist.cdf( 0.5 );
// returns ~0.003
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- TODO: better examples -->

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

```javascript
var objectKeys = require( '@stdlib/utils/keys' );
var invgamma = require( '@stdlib/stats/base/dists/invgamma' );

console.log( objectKeys( invgamma ) );
```

</section>

<!-- /.examples -->

<section class="links">

[invgamma-distribution]: https://en.wikipedia.org/wiki/Inverse_Gamma_distribution

<!-- <toc-links> -->

[@stdlib/stats/base/dists/invgamma/ctor]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/ctor

[@stdlib/stats/base/dists/invgamma/entropy]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/entropy

[@stdlib/stats/base/dists/invgamma/kurtosis]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/kurtosis

[@stdlib/stats/base/dists/invgamma/mean]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/mean

[@stdlib/stats/base/dists/invgamma/mode]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/mode

[@stdlib/stats/base/dists/invgamma/skewness]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/skewness

[@stdlib/stats/base/dists/invgamma/stdev]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/stdev

[@stdlib/stats/base/dists/invgamma/variance]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/variance

[@stdlib/stats/base/dists/invgamma/cdf]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/cdf

[@stdlib/stats/base/dists/invgamma/logpdf]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/logpdf

[@stdlib/stats/base/dists/invgamma/pdf]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/pdf

[@stdlib/stats/base/dists/invgamma/quantile]: https://github.com/stdlib-js/stats/tree/main/base/dists/invgamma/quantile

<!-- </toc-links> -->

</section>

<!-- /.links -->
