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From "Olga Natkovich (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1150) VAR() Variance UDF
Date Wed, 17 Mar 2010 00:23:27 GMT

    [ https://issues.apache.org/jira/browse/PIG-1150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12846229#action_12846229
] 

Olga Natkovich commented on PIG-1150:
-------------------------------------

We would like to cut release branch next Monday. This mean that the code needs to be committed
by the end of the week. Is this likely to happen?

If not, I would like to unlink this from 0.7.0 release and leave for inclusion in one of the
future releases when this patch is ready.

> VAR() Variance UDF
> ------------------
>
>                 Key: PIG-1150
>                 URL: https://issues.apache.org/jira/browse/PIG-1150
>             Project: Pig
>          Issue Type: New Feature
>    Affects Versions: 0.5.0
>         Environment: UDF, written in Pig 0.5 contrib/
>            Reporter: Russell Jurney
>             Fix For: 0.7.0
>
>         Attachments: var.patch
>
>
> I've implemented a UDF in Pig 0.5 that implements Algebraic and calculates variance in
a distributed manner, based on the AVG() builtin.  It works by calculating the count, sum
and sum of squares, as described here: http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Parallel_algorithm
> Is this a worthwhile contribution?  Taking the square root of this value using the contrib
SQRT() function gives Standard Deviation, which is missing from Pig.

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