# How to take the average of each column of a matrix without including a certain number

12 views (last 30 days)
Hail on 16 Jul 2014
Commented: Image Analyst on 16 Jul 2014
I have a matrix that has 864 rows and 7 columns and is filled with positive numbers and zeros. I want to take the average of each of those columns. However when MATLAB is taking the averages, I dont want it to include the zeros in its calculations. Can this be done?

Joseph Cheng on 16 Jul 2014
What you can do is do a quick substitution. if you know your matrix doesn't have any NaN (Not a number) then substitute the 0's for nan and then use the nanmean() which will exclude the NaNs from the average.
B=A;
B(A==0)=nan;
NonZeroAverages = nanmean(B);
Hail on 16 Jul 2014
Thanks

Image Analyst on 16 Jul 2014
If you don't have nanmean because you don't have the Finance or Statistics toolbox, you can simply do
columnMeans = sum(a, 1) ./ sum(a~=0);
where "a" is the name of your matrix. This sums up the values in each column, then divides it by the sum of the non-zero values in each column.
Image Analyst on 16 Jul 2014
Even if you do have those toolboxes, I'd use this method instead.

Sara on 16 Jul 2014
my_mean = zeros(size(a,2),1);
for i = 1:size(a,2)
d = a(:,i);d = d(d~=0);
my_mean(i) = mean(d);
end
Hail on 16 Jul 2014
thanks

### Categories

Find more on Descriptive Statistics and Visualization in Help Center and File Exchange

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by