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https://issues.apache.org/jira/browse/PIG-1150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12903581#action_12903581
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Olga Natkovich commented on PIG-1150:
-------------------------------------
Dmitry, are you planning to add unit tests? Do we still want this in for 0.8?
(Since it is going into piggybank, we can do this post branching but then we
need to test in 2 places.)
> 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
> Assignee: Dmitriy V. Ryaboy
> Fix For: 0.8.0
>
> 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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