Alan Gates commented on PIG-1150:

We've had some requests to add a fixed point type for issues where precision 
problems aren't acceptable.  Another option for you would be to add the 
variance now in double and when a fixed point type is added add a fix point 
version of variance.

> 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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