| From: | Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at> |
|---|---|
| To: | "'Jeroen van Vianen'" <jeroen(at)design(dot)nl>, "'pgsql-hackers(at)postgreSQL(dot)org'" <pgsql-hackers(at)postgreSQL(dot)org> |
| Subject: | AW: [HACKERS] Implementing STDDEV and VARIANCE |
| Date: | 2000-01-24 10:53:45 |
| Message-ID: | 219F68D65015D011A8E000006F8590C603FDC215@sdexcsrv1.f000.d0188.sd.spardat.at |
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| Lists: | pgsql-hackers |
> 2. I am proposing the names stddev(x) and variance(x) for
> population and
> samplestddev(x) and
> samplevariance(x) for sample statistics. Any comments?
Other db's have:
stdev() for standard deviation sample (N-1)
variance() for variance computed from a sample (N-1)
> 3. I'm planning to implement this for types float4, float8
> and numeric. Any
> other types also? int[2,4,8] don't seem logical, as these
> would introduce
> serious rounding errors.
Integer would be good also. Do the arithmetic in numeric
to avoid loss of precision.
Andreas
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