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From "Paul Cowan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-178) Implement Zipf distribution
Date Wed, 23 Jan 2008 00:22:34 GMT

    [ 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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