From: | "Stupor Genius" <stuporg(at)erols(dot)com> |
---|---|
To: | "Hackers" <pgsql-hackers(at)postgresql(dot)org> |
Cc: | "Bruce Momjian" <maillist(at)candle(dot)pha(dot)pa(dot)us> |
Subject: | RE: [HACKERS] Standard Deviation function. |
Date: | 1998-06-05 03:22:09 |
Message-ID: | 000001bd9031$1fe5e800$d39daccf@darren |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
> > > I really need a Standard Deviation aggregate function...
> >
> > 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.
>
> I remember talking about this to someone, and the problem is that you
> needed the average WHILE scanning through the table, which required two
> passes, which the aggregate system is not designed to do. I may be
> wrong on this, though.
I had asked you how to calculate this and the variance early last
year. One (I think the variance) was two-pass because of the need
for the average, but I thought the StdDev would work with the struct.
Been a while and I still haven't configured #(*&^ FreeBSD ppp yet.
darrenk
From | Date | Subject | |
---|---|---|---|
Next Message | Bruce Momjian | 1998-06-05 03:24:16 | Re: [HACKERS] Standard Deviation function. |
Previous Message | Bruce Momjian | 1998-06-05 01:55:07 | Re: [HACKERS] Standard Deviation function. |