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Date: Tue, 22 Jan 2008 16:22:34 -0800 (PST)
From: "Paul Cowan (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Subject: [jira] Commented: (MATH-178) Implement Zipf distribution
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    [ https://issues.apache.org/jira/browse/MATH-178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12561530#action_12561530 ] 

Paul Cowan commented on MATH-178:
---------------------------------

Further to this: there's an interesting definition at http://functions.wolfram.com/GammaBetaErf/HarmonicNumber2/03/01/01/0008/ which is based on polygamma (there's an implementation of THAT in Gnu GSL? Not sure if that's useful?) but that in turn requires calculating the factorial of the exponent (which is in turn slow, though easily cacheable) and also requires restricting the exponent to a natural number, which is fine for us but may make the ZipfDistribution less useful for others.

> Implement Zipf distribution
> ---------------------------
>
>                 Key: MATH-178
>                 URL: https://issues.apache.org/jira/browse/MATH-178
>             Project: Commons Math
>          Issue Type: New Feature
>            Reporter: Paul Cowan
>            Priority: Minor
>         Attachments: ZipfDistribution.patch, ZipfDistribution2.patch
>
>
> Per my post to commons-dev -- http://mail-archives.apache.org/mod_mbox/commons-dev/200801.mbox/%3c478EDFEB.3010902@funkwit.com%3e -- I'd like to propose adding a Zipf distribution to commons-math.
> I have a patch, but it's incomplete and somewhat inefficient; I'd like to throw it up for discussion though. To follow.

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