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Re: matrix addition skipping nan values


From: Naveen Garg
Subject: Re: matrix addition skipping nan values
Date: Sat, 19 Dec 2009 13:28:18 -0500

On Sat, Dec 19, 2009 at 12:27 PM, Søren Hauberg <address@hidden> wrote:
lør, 19 12 2009 kl. 12:02 -0500, skrev Naveen Garg:
> I would like to do element wise addition over matrices while skipping
> NaN values. there is nansum, but it does column wise addition within a
> matrix.

I don't quite follow what you mean by "skipping" NaN values. Do you
simply want to let NaN's work like zeros? If so, you should be able to
do something like (untested code)

 a (isnan (a)) = 0;
 b (isnan (b)) = 0;
 c = a + b;

Søren

sort of.

a_fixed = a;
a_fixed
(isnan(a)) = 0;
b_fixed
= b;
b_fixed
(isnan(b)) = 0;
c
= a_fixed.+b_fixed;

c(and(isnan(a), isnan(a))) = NaN

works. 



sorry for the double post, but someone also posted a solution using nansum here: http://stackoverflow.com/questions/1933455/matrix-addition-skipping-nan-values



by the way, numpy has a multidimensional version of the label function.  I will translate as soon as i need to use it in octave. 


Thanks.

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