How to do a nanmean not including zero values.

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HA
HA 2019-12-20
编辑： Matt J 2019-12-20
Hello,
I have some awkward sea ice data, where I need to do some averaging of just the none zero values.
Land values are NAN and I would like to keep them as such, and ocean values are zeros. I would like to do some monthly averaging between years, which I would normally do as-
siz = size(A) ;
B = zeros(siz(1), siz(2), siz(3), 12) ;
for mId = 1 : 12
B(:,:,:,mId) = nanmean(A(:,:,:,mId:12:end), 4) ;
end
Normally I would just set all zero values to NAN for this, however, I need to keep them as zero for my file to work further down the line.
Thank you,
Holly
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J. Alex Lee
J. Alex Lee 2019-12-20
It does sound like just ignoring zeros...so if the tabular storage works for you, instead of
'mean'
I guess you'd want to use something like
@(x)mean(x(x~=0),2,'omitnan')
where dimension 2 assumes you're operating a table column
I agree it would be nice if your data can be converted to the more meaningful timetable and operations look more human readable...
...But to the original question, I might be interpreting way too simplistically, but just in case, is it as simple as making a copy of A to modify for purposes of averaging, and using the original A downstream?
Guillaume
Guillaume 2019-12-20
While we're at it, note that the original code can be simplified to
B = mean(reshape(A, size(A, 1), size(A, 2), size(A, 3), 12, []), 5, 'omitnan');

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回答（1 个）

Matt J
Matt J 2019-12-20
编辑：Matt J 2019-12-20
Normally I would just set all zero values to NAN for this, however, I need to keep them as zero for my file to work further down the line.
I don't see what prevents you from simply modifying a copy of A instead of A itself,
siz = size(A) ;
Atmp=reshape(A,siz(1), siz(2), siz(3), 12,[]);
Atmp(A==0)=nan;
B=mean(Atmp,5,'omitnan');

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