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RE: [HACKERS] Standard Deviation function.

From: "Stupor Genius" <stuporg(at)erols(dot)com>
To: "Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: RE: [HACKERS] Standard Deviation function.
Date: 1998-06-05 01:35:56
Message-ID: 000001bd9022$48ee3360$ad99accf@darren (view raw or flat)
Thread:
Lists: pgsql-hackers
> I really need a Standard Deviation aggregate function...
> 
> I know about the man pages for "create aggregate" and "create
> function".  Is there something else I should look at?
> 
> It seems kind of hard to do with only two state functions unless
> I "cheat".  I need to keep three values, Count, Sum, and Sum of
> Squares.
> 
> Any hints or advice??

I thought about this a long time ago and had an idea but never
got around to trying to implement it.  I was going to have some
functions that worked on a structure of two doubles to track
the sum and square instead of using only one simple type.

darrenk

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Subject: Re: [HACKERS] Standard Deviation function.
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Subject: Standard Deviation function.

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