Re: Weighted Stats

On Fri, Mar 18, 2016 at 06:12:12PM -0700, Jeff Janes wrote:
> On Tue, Mar 15, 2016 at 8:36 AM, David Fetter <david(at)fetter(dot)org> wrote:
> >
> > Please find attached a patch that uses the float8 version to cover the
> > numeric types.
>
> Is there a well-defined meaning for having a negative weight? If no,
> should it be disallowed?

Done.

> Shouldn't these then give the same result:
>
> select stddev_samp(val) from foo;
> stddev_samp
> -------------------
> 2887.054977297105
>
> select weighted_stddev_samp(val,count) from foo2;
> weighted_stddev_samp
> ----------------------
> 2887.19919651336
>
> The 5th digit seems too early to be seeing round-off error.

Fixed down-thread.

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david(dot)fetter(at)gmail(dot)com

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