# How do I exclude NaN values when calculating mean of each row in a matrix?

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Jillian Sweatt 2017년 9월 8일
댓글: Jason Stockton 2021년 8월 9일
gpd=[2014,3.320,3.364,3.532,3.659,3.691,3.695,3.633,3.481,3.403,...
3.182,2.887,2.560;2015,2.110,2.249,2.483,2.485,2.775,2.832,...
2.832,2.679,2.394,2.289,2.185,2.060;2016,1.967,1.767,1.958,...
2.134,2.264,2.363,2.225,2.155,2.208,2.243,2.187,2.230;2017,...
2.351,2.299,2.323,2.418,2.386,2.337,2.281,NaN,NaN,NaN,NaN,NaN];
for a=gpd(:,end)
y=mean(a,2);
end
The output for the last row of y returns NaN (a copy of the command window is shown below). How do you exclude the NaN values in the last row in order to output an average of all the real number values?
>>y =
2.5600
2.0600
2.2300
NaN

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### 답변(4개)

Guillaume 2017년 9월 8일
Since version 2015a, the max, min, mean, median, sum, var, std, and cov function have included a flag to ignore nans
y = mean(gpd, 2, 'omitnan')
Note that your loop makes no sense at all. It's averaging just the last column, so not doing any averaging at all. The line above will average all the columns.
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José-Luis 2017년 9월 8일
y = nanmean(a,2)
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Jason Stockton 2021년 8월 9일
Note: Matlab Help says nanmean() is not recommended. They recommend using mean() with the 'omitnan' flag like Guillaume shows.
They may plan to remove it in the future. Personally, I like nanmean better.

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OCDER 2017년 9월 8일
편집: OCDER 2017년 9월 8일
Remove the for loop, as it only does the last column, which can't be averaged.
To take mean with NaN's in it, use José-Luis' suggestion of nanmean (voted your answer up :) ).
y = nanmean(gpd, 2)
This will return a 5x1 matrix of average of gdp for each row.
y =
158.0313
157.2595
157.0539
254.1744
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OCDER 2017년 9월 8일
편집: OCDER 2017년 9월 8일
Actually, I'm looking at your code and this for loop may not be needed:
for a = gpd(:, end)
... %This only does one iteration, where a = last column.
end
In this case, José-Luis' suggestion of nanmean is correct.

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Changoleon 2018년 3월 5일
https://www.mathworks.com/help/stats/nanmean.html

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