ignoring NAs in a dataset with numpy

Robert Kern robert.kern at gmail.com
Tue Oct 28 20:34:43 CET 2008


mrafi wrote:
> Hey All,
> I am working with numpy 
> I have a data set with a lot of nan values, and i want to calculate standard
> deviation
> is there a direct function to do it for example nansum(or something like
> this),
> to calculate standard deviation ignoring nan values??

You will want to ask numpy questions on the numpy-discussion mailing list.

   http://www.scipy.org/Mailing_Lists

scipy.stats.nanstd() implements this. Additionally, data[~isnan(data)].std() 
works unless if you need to apply the std() along just one axis.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco




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