154 lines
6.2 KiB
Markdown
154 lines
6.2 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Inverse Gamma
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> Inverse gamma distribution.
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<section class="usage">
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## Usage
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```javascript
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var invgamma = require( '@stdlib/stats/base/dists/invgamma' );
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```
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#### invgamma
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Inverse gamma distribution.
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```javascript
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var dist = invgamma;
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// returns {...}
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```
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The namespace contains the following distribution functions:
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<!-- <toc pattern="*+(cdf|pdf|mgf|quantile)*"> -->
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<div class="namespace-toc">
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- <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>
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- <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>
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- <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>
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- <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>
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</div>
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<!-- </toc> -->
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The namespace contains the following functions for calculating distribution properties:
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<!-- <toc pattern="*+(entropy|kurtosis|mean|median|mode|skewness|stdev|variance)*"> -->
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<div class="namespace-toc">
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- <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>
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- <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>
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- <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>
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- <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>
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- <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>
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- <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>
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- <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>
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</div>
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<!-- </toc> -->
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The namespace contains a constructor function for creating a [inverse gamma][invgamma-distribution] distribution object.
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<!-- <toc pattern="*ctor*"> -->
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<div class="namespace-toc">
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- <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>
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</div>
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<!-- </toc> -->
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```javascript
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var InvGamma = require( '@stdlib/stats/base/dists/invgamma' ).InvGamma;
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var dist = new InvGamma( 2.0, 4.0 );
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var y = dist.cdf( 0.5 );
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// returns ~0.003
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```
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</section>
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<!-- /.usage -->
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<section class="examples">
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## Examples
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<!-- TODO: better examples -->
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<!-- eslint no-undef: "error" -->
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```javascript
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var objectKeys = require( '@stdlib/utils/keys' );
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var invgamma = require( '@stdlib/stats/base/dists/invgamma' );
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console.log( objectKeys( invgamma ) );
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[invgamma-distribution]: https://en.wikipedia.org/wiki/Inverse-gamma_distribution
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<!-- <toc-links> -->
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[@stdlib/stats/base/dists/invgamma/ctor]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/ctor
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[@stdlib/stats/base/dists/invgamma/entropy]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/entropy
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[@stdlib/stats/base/dists/invgamma/kurtosis]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/kurtosis
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[@stdlib/stats/base/dists/invgamma/mean]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/mean
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[@stdlib/stats/base/dists/invgamma/mode]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/mode
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[@stdlib/stats/base/dists/invgamma/skewness]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/skewness
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[@stdlib/stats/base/dists/invgamma/stdev]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/stdev
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[@stdlib/stats/base/dists/invgamma/variance]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/variance
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[@stdlib/stats/base/dists/invgamma/cdf]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/cdf
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[@stdlib/stats/base/dists/invgamma/logpdf]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/logpdf
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[@stdlib/stats/base/dists/invgamma/pdf]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/pdf
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[@stdlib/stats/base/dists/invgamma/quantile]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dists/invgamma/quantile
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<!-- </toc-links> -->
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</section>
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<!-- /.links -->
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