need an empty space in a column

I have a matrix like this

1  4
2  5
3  2
4  0
5  6
6  1

Now I want to delete the 0 from the column 2 but if I delete this the corresponding position is beibg deleted and 6 is coming to this place. but I need the 0 should be deleted and it will also keep the space blan. It would look like

1  4
2  5
3  2
4  
5  6
6  1

how to solve the problem?

thanks in advance

Answer 1

[Andrei Bobrov]

a = [1  4
2  5
3  2
4  0
5  6
6  1];

a(a(:,2) == 0,2) = nan;

[Moon Datta]

Thank you Sir