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https://issues.apache.org/jira/browse/PIG-1150?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Russell Jurney updated PIG-1150:
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    Attachment: var.patch

This patch will not cut the mustard - it lacks Javadoc, and test cases and its 
just plain ugly.

That being said, people requested this on twitter, so I'm pushing this one for 
people to use if they want to.  Will get a passable patch up later this week.

> 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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