# how to calcuate mean with NaN

조회 수: 7(최근 30일)
Peihong 2013년 9월 12일
댓글: Esen S. 2020년 4월 21일
Dear Friend,
There are two matrixs with the same size, there are some NaNs in each matrix. I want to calculate the mean of corresponding datapoints, which might contain NaN. for example, A(1,2)=NaN, B(1,2)=3, I need the average of the sum of 3+NaN divided by the effective number of data points, here is 1 since A(1,2) is NaN, to be 3. If A(2,2)=2,B(2,2)=5, I need the average to be (2+5)divided by 2, which equals 3.5 since neither A(2,2) and B(2,2) contains NaN. Is there a way to achieve this goal without using a for loop? thanks

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### 채택된 답변

Sven 2013년 9월 12일
편집: Sven 2013년 9월 12일
If you have the Statistics Toolbox, just replace calls to mean() with calls to nanmean().
If you don't have it, you can do the same by downloading the File Exchange contribution nansuite
Here's an example:
A = reshape(1:4,2,2);
B = A + 10;
A([1 3]) = nan % Set some NaNs
B([1 2]) = nan
yourMean = nanmean(cat(3,A,B),3)
Which results in:
A =
NaN NaN
2 4
B =
NaN 13
NaN 14
yourMean =
NaN 13
2 9
##### 댓글 수: 1표시 없음숨기기 없음
Peihong 2013년 9월 12일
Hi, Sven, thanks a lot. It's exactly what I need.

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### 추가 답변(2개)

Jan 2013년 9월 12일
Emulating NANMEAN without the statistics toolbox is easy:
index = isnan(X);
X(index) = 0;
M = sum(X, 2) ./ sum(index, 2);
##### 댓글 수: 1표시 없음숨기기 없음
Esen S. 2020년 4월 21일
I belive there is a tilde missing in the last line.
It should be M = sum(X, 2) ./ sum(~index, 2);

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Shashank Prasanna 2013년 9월 12일

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