MATLAB: How to find columns with all zeros in the matrix

columnsmatrixnonzero entrieszero

I've got a large matrix A and would like to find out if any of the columns contain only zeros. I've found a solution for finding all the rows with only zeros but I'm not sure how to make it all columns.

Also, would there be a way to find out which columns have exactly 4 or 3 or 2 or X nonzero entries?

Best Answer

cols_with_all_zeros = find(all(A==0)); % all zeros
cols_with_3_nonzeros = find(sum(A~=0)==3); % exactly 3 non-zeros

Related Solutions

MATLAB: How to store [row,col]= find(X==a) results in a N*2 matrix ?!

Unless I’m missing something in your Question, I would create an (Nx2) matrix of the row and column indices as:

[row,col]= find(X==3);
Index_Mtx = [row col];

MATLAB: How to chose random row which contain non-zero element

I would first find the non-zero rows, then choose randomly amongst them:

nzr = find(sum(A,2)>0);                             % Indices Of Non-Zero Rows
random_nz_row = nzr(randi(length(nzr), 1))          % Choose One Non-Zero Row
nz_row = A(random_nz_row,:)                         % Display Random Non-Zero Row

Best Answer

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MATLAB: How to store [row,col]= find(X==a) results in a N*2 matrix ?!

MATLAB: How to chose random row which contain non-zero element

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