| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | iz(at)sai(dot)msu(dot)ru |
| Cc: | "Brendan Jurd" <direvus(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: No stddev() for interval? |
| Date: | 2006-05-20 16:34:47 |
| Message-ID: | 11541.1148142887@sss.pgh.pa.us |
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| Lists: | pgsql-general |
"Ivan Zolotukhin" <ivan(dot)zolotukhin(at)gmail(dot)com> writes:
> On 5/20/06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Is it sensible to calculate standard deviation on intervals? How would
>> you handle the multiple components? I mean, you could certainly define
>> *something*, but how sane/useful would the result be?
> Strictly speaking there's nothing bad in intervals. Physically
> standart deviation on interval can be very useful without any doubts.
If the intervals are all expressed in seconds then sure, the calculation
is straightforward and useful. I'm wondering what happens when nonzero
values of days and months get in there.
regards, tom lane
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