How to add a diagonal to a matrix?

I have the following matrix M=[1 2 3; 4 5 6 ] and I would like to transform it to the follwowing matrix M=[0 1 2; 3 0 4; 5 6 0].

How to do it? It is how to add a zero diagonal to a predefined matrix?

Answer 1

[Matt J]

One way,

[J,I]=ndgrid(1:size(M,1)+1);
idx=(I~=J);

M = accumarray([I(idx),J(idx)],reshape(M.',[],1))

M =

     0     1     2
     3     0     4
     5     6     0

[Nadia_Ny635]

Thank you so much

[Matt J]

You're quite welcome, but please Accept-click the answer if it resolves your question.