Hi everyone, I need your help on ouple of questions. I need to do summation on a three dimensional array.

My array has 59 rows, 77 columns and360 months. I need to get sum of 3 months for all 360 months so that I will have 59*77*120 matrix. What I did is the following;

k=matrix (:,:,1);
for j=1:length(matrix);
sumof3months(:,:,j)=sum(matrix(:,:,k:k+2));
k=k+3
end

Question two

I have 59x77x360 matrix. I need to do integration over the third dimension.

Intmatrix=integral (matrix,1,360)

Answer 1

[Walter Roberson]

 sumof3months =  matrix(:,:,1:3:end) + matrix(:,:,2:3:end) + matrix(:,:,3:3:end);

 Intmatrix = trapz(matrix, [], 3);

[Engdaw Chane]

Thank you Walter! That is helpful. My matrix has 59 rows, 77 columns and 120 months.

Now, I need to calculate the probability of a value (0 rainfalls) for each row and column.

What I did is;

count=numel(sumof3months20_50(:,:,:),0) % count number of zeros
probabilityofzero=count(:,:,:)./120;

[Walter Roberson]

mask = sumof3months20_50 == 0;
probabilityofzero = sum(mask, 3) ./ size(mask,3);

[Engdaw Chane]

Walter, thank you very much for your kindness! Cheers!