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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-249) Gamma incomplete
Date Mon, 16 Mar 2009 22:33:50 GMT

    [ https://issues.apache.org/jira/browse/MATH-249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12682490#action_12682490
] 

Luc Maisonobe commented on MATH-249:
------------------------------------

Could you check if this simple implementation provides good enough results :

{code}
public static double incompleteGamma(double a, double x) {
    return regularizedGammaQ(a, x) * Math.exp(logGamma(a));
}
{code}

this is basically the inversion of equation (2) in [http://mathworld.wolfram.com/RegularizedGammaFunction.html]
If so, I'll check it in.

> Gamma incomplete
> ----------------
>
>                 Key: MATH-249
>                 URL: https://issues.apache.org/jira/browse/MATH-249
>             Project: Commons Math
>          Issue Type: New Feature
>    Affects Versions: 2.0
>            Reporter: Gilles
>            Priority: Minor
>
> Hello.
> In the class "special.Gamma", there seem to be no explicit way to obtain the incomplete
gamma function.[1]
> Could you provide it?
> Thanks,
> Gilles
> [1] http://mathworld.wolfram.com/IncompleteGammaFunction.html

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