# How to make a loop through each row?

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Daria Ivanchenko on 21 Oct 2020
Commented: David Hill on 21 Oct 2020
Hi! I have a variable A in the size of 50x15000 with different numbers. And I have variable B, the same size 50x15000, that has only zeros and ones. I want to filter the data in the variable A based on variable B, and put the result in variable C. I need to take the numbers from A only if it is zero in the matrix B. One row is one trial in both A and B.
I wrote a small for loop:
C = NaN(size(A));
for i = 1:size(A,1)
C(i,:) = A(i, B(i,:) == 0);
end
The problem is that, after filtering the data, each row has different number of columns, so it doesn't want to be in one matrix. I have a message like this: "Unable to perform assignment because the size of the left side is 1-by-15000 and the size of the right side is 1-by-13683".
How can I solve this problem?
Thank you!
##### 2 CommentsShow 1 older commentHide 1 older comment
Daria Ivanchenko on 21 Oct 2020
A matrix padded with NaN would be better!

David Hill on 21 Oct 2020
Edited: David Hill on 21 Oct 2020
Make C a cell array
for i = 1:size(A,1)
C{i} = A(i, B(i,:) == 0);
end
##### 2 CommentsShow 1 older commentHide 1 older comment
David Hill on 21 Oct 2020
C=zeros(size(A));
C(B==0)=A(B==0);
C(B==1)=nan;