ODFF1.2 GEOMEAN

[Eike Rathke]

Hi Winfried,

On Thursday, 2017-09-14 09:18:23 +0200, Winfried Donkers wrote:

> As we now have changed GEOMEAN, I think it would be wise to try to improve ODFF1.2 as well for GEOMEAN.
> 
> Verzonden: woensdag 26 juli 2017 12:06
> 
> Geometric mean is defined as n-root( a1 * a2 * ... * an). This applies for n positive values a#.
> This is awkward to compute as overflow is lurking in case of large values a and a large number n.
> An alternative computation is given in ODFF, but the case of any value a# being 0 is not mentioned (result is then 0).
> Any a# with value is a geometrically valid situation, unlike negative values which do not have any geometric meaning AFAIK.
> 
> I would propose an amendment of ODFF1.2 for GEOMEAN:
> Constraints: numbers >= 0
> Semantics: addition of Returns zero when one or more numbers have value 0.
> 
> What's your opinion?

Isn't it rather that the product of all a# must be >=0 because of the
rootN?

Without reading statistics I have no idea if a single negative value may
make sense for GEOMEAN or is actually an error (like it is treated today
by both Calc and Excel). Do you happen to know?

  Eike

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