MATLAB: Remove column in matrix

Question

I would like to remove rows and columns which are empty (contains more zeros than value) : for example

A=[0 0 0 0; 0 1 2 0; 8 5 8 2;5 8 2 7;0 1 0 0; 0 0 0 0]

to give output as

B=[5 8; 8 2]

Answer 1

nz = logical(A);
B = A(sum(nz,2) >= size(A,2)/2, sum(nz) >= size(A,1)/2);

You will notice this gives a 3 x 2 array, not a 2 x 2 array. The row 0 1 2 0 does not have more 0 than values, so it needs to be kept.

If you change the rules to say that you are not to keep something unless the number of values exceeds 1/2 of the possible, then you need to eliminate the third column of A, [0; 2; 8; 2; 0; 0] because in that case 3 entries out of 6 are populated and 3 does not exceed (6/2)