# Make specific columns of a matrix zero.

6 views (last 30 days)
Santos García Rosado on 4 Mar 2021
Hi Mathworks community!
So I have a matrix A such as:
A = [1,2,3,4,5,6,7,8,9; 5,8,6,44,8,6,8,7,3; 9,8,7,6,5,4,3,2,1]
And an array b that specifies the columns I' DON´T want to make zero:
b = [1,4,5,9]
Getting an output such as:
out = [1,0,0,4,5,0,0,0,9; 5,0,0,44,8,0,0,0,3; 9,0,0,6,5,0,0,0,1]
I'm working with much bigger dimensions so, Any ideas of how to do this efficiently?
Thank you!
Santos

Stephen23 on 4 Mar 2021
A = [1,2,3,4,5,6,7,8,9; 5,8,6,44,8,6,8,7,3; 9,8,7,6,5,4,3,2,1];
b = [1,4,5,9];
out = zeros(size(A));
out(:,b) = A(:,b)
out = 3×9
1 0 0 4 5 0 0 0 9 5 0 0 44 8 0 0 0 3 9 0 0 6 5 0 0 0 1
Santos García Rosado on 4 Mar 2021
Thank you Stephen! Exactly what I was looking for.

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