[jira] [Resolved] (STATISTICS-23) Parameter names in "GammaDistribution"

["Gilles Sadowski (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/STATISTICS-23?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gilles Sadowski resolved STATISTICS-23.
---------------------------------------
    Resolution: Fixed

Fixed in commit cbc1059a5156bbb1bb2b96d6ea323fd3ec601e05 ("master" branch).

> Parameter names in "GammaDistribution"
> --------------------------------------
>
>                 Key: STATISTICS-23
>                 URL: https://issues.apache.org/jira/browse/STATISTICS-23
>             Project: Apache Commons Statistics
>          Issue Type: Bug
>          Components: distribution
>            Reporter: Gilles Sadowski
>            Assignee: Gilles Sadowski
>            Priority: Critical
>
> After upgrading to v1.3 of "Commons RNG", a unit test for {{GammaDistribution}} fails:
> {noformat}
> [ERROR]   GammaDistributionTest>ContinuousDistributionAbstractTest.testSampler:342 Chisquare test failed p-value = 1.1102230246251565E-15 chisquare statistic = 72.63199999999999. 
> value   expected        observed
> 1       250             355
> 2       250             183
> 3       250             200
> 4       250             262
> {noformat}
> It is caused by the inversion of the parameters when instantiating the sampler (at line ):
> {code:java}
>     public ContinuousDistribution.Sampler createSampler(final UniformRandomProvider rng) {
>         // Gamma distribution sampler.
>         return new AhrensDieterMarsagliaTsangGammaSampler(rng, scale, shape)::sample;
>     }
> {code}
> Things are back to normal when switching the {{scale}} and {{shape}} arguments.



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