How to force nansum(NaN+ NaN) = NaN, not 0 ?
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Alex Kurek
am 5 Jan. 2016
Bearbeitet: Stephen23
am 5 Jan. 2016
Hello,
I need to sum some multidimentional arrays after SPMD processing. This arrays contains also NaNs, but I need to computer a proper mean value of them later. Since:
>> nansum(NaN + NaN)
ans =
0
This case will affect the result. How to perform such a summing, but sum of ONLY NaNs has to be equal to NaN (not zero!)?
Best regards, Alex
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Stephen23
am 5 Jan. 2016
Bearbeitet: Stephen23
am 5 Jan. 2016
Just keep track of where all elements are NaN, and replace their sum with NaN after using nansum. You should be able to adapt this example to help you, it sums along each column:
>> A = [1,2,NaN,NaN;3,NaN,4,NaN]
A =
1 2 NaN NaN
3 NaN 4 NaN
>> B = [6,7,8,NaN;9,NaN,NaN,NaN]
B =
6 7 8 NaN
9 NaN NaN NaN
>> C = nansum(A+B,1)
C =
19 9 0 0
>> C(all(isnan(A)&isnan(B),1)) = NaN
C =
19 9 0 NaN
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