MATLAB: I have an all zero matrix ‘a’ of size m x n. In a new 2 column matrix ‘b’ I have the indices where I should replace the zero in ‘a’ with 1. Is there a way to do this without a ‘for’ loop? The m,n > 500..

matrix array

The question above.

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sparse() is the easiest way to handle this. Another way is

A( sub2ind(size(A),B(:, 1),B(:, 2)) = 1;

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MATLAB: What is the elegent way to replace every Nth column in a matrix with another column

           B = randn(10,10);
           % replace every 3rd column with x
           x = randn(10,1);
           N = 3;
           indices = 1:N:size(B,2);
           x = repmat(x,1,length(indices));
           B(:,indices) = x;

Probably you are trying to replace a matrix which you get with A(:,1:n:end) with a vector. The sizes have to match.

MATLAB: Insert zero column in a m×n matrix

For a given matrix A:

A = rand(5,5);

Using square braces to concatenate:

A_zeros = [zeros(size(A,1),1) A];

Using the cat() command:

A_zeros = cat(2, zeros(size(A,1),1), A);

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MATLAB: What is the elegent way to replace every Nth column in a matrix with another column

MATLAB: Insert zero column in a m×n matrix

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