Help with matrix manipulation in matlab

I have a matrix M with dimension 600x500. I want to do an average of its values along vertical direction, in order to have a matrix with smaller dimension. For example, I want to obtain a matrix with dimension 200x500: this means that, every three values along each column, I take just one (which is the average of the three values). How can I do this ? Thanks!

Answer 1

[Andrei Bobrov]

out = squeeze(mean(reshape(M,3,[],size(M,2))));

[aurc89]

Thanks!