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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2020/09/28 15:26:51 UTC

[GitHub] [arrow] nealrichardson commented on pull request #8269: ARROW-10070: [C++][Compute] Implement stdev aggregate kernel

nealrichardson commented on pull request #8269:
URL: https://github.com/apache/arrow/pull/8269#issuecomment-700081921


   Two notes:
   
   1. Naming: I've never seen this called `stdev` anywhere. `stddev` is common, in numpy and julia it's `std`, in R it's `sd`. Let's go with one of those. Maybe just add an extra "d"?
   2. Since `sd = sqrt(var)` (https://github.com/apache/arrow/pull/8269/files#diff-461bd7e445c2a190f1173ebdefa21002R106), would it make sense to implement variance (i.e. most of this patch), and then standard deviation as the sqrt of that? That way we get two kernels (or even three, if sqrt is exposed as a kernel too).


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