Details
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Wish
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Status: Resolved
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Minor
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Resolution: Duplicate
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None
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None
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Description
The last step in the unholy triumvirate of statistical built-ins is the variance. We already have the n (count) and the mean (avg). I currently have a job or two that filters all of the data into a single reducer which just computes mean/n/variance and writes it to a table...so my guess is that this would be a pretty big speed increase. Not a huge deal though, as computing the variance myself is trivial.
(Average, variance, and n can be co-computed in one pass, so if you're doing var() you can basically have avg() and count() for free.)
