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Hive, mail # user - Built - In Aggregate Function - Standard Deviation


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Matt Pestritto 2009-05-26, 20:02
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Re: Built - In Aggregate Function - Standard Deviation
Amr Awadallah 2009-05-27, 08:24
I agree that a builtin for std dev is a good idea.

that said, you can achieve this easy in one pass, just use:

select sum( pow(col,2) ) as totsqr, sum( col ) as tot, count(1) as n,
pow( (n*totsqr - pow(tot,2) )/(n*(n-1)), 0.5) as stddev
from ....

Matt Pestritto wrote:
> Hi.
>
> Are there plans to write a standard deviation aggregate function ?  I
> had to build my own which translated into multiple hive queries.  
> While it works, a build-in function would have been much easier.
>
> Thanks
> -Matt
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Matt Pestritto 2009-05-30, 23:08
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Zheng Shao 2009-05-30, 23:22
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Amr Awadallah 2009-05-31, 07:04
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Zheng Shao 2009-05-31, 09:35