[SciPy-dev] semantics of stats.stats.nanstd

Alexandre Fayolle alexandre.fayolle at logilab.fr
Thu Aug 11 14:58:16 CDT 2005


I'm working on the problem reported
http://www.scipy.net/roundup/scipy/issue243, and I'm wondering if the
patch I submitted implements the expected semantics for nanstd()

The question is : shall the function simply discard the nan values, or
should it consider that a population with nan values become a sample of
the population, and change the value of the denominator. 

To put it otherwise, is it expected that 

nanstd([nan, 2, 3, 4,], bias=0) == std([2, 3, 4], bias=0) 
                                or std([2, 3, 4], bias=1) 

or some other value ?

The patch I sent assumes the first option, but Alexander Perry pointed
out that the second option may be what is expected. 
 
-- 
Alexandre Fayolle                              LOGILAB, Paris (France).
http://www.logilab.com   http://www.logilab.fr  http://www.logilab.org
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