"Restart" elements of a matrix

Hi! I have a couple of matrix (all squares and sorted by rows) like this:

A=[1 2 3; 4 5 6; 7 8 9]

And I need to, from any specific element, restart the sequence. For example:

A=[1 2 3; 1 2 3; 4 5 6]

Any ideas? Thanks a lot!

Answer 1

[Matt J]

   restart=4; % your example

   N=numel(A);
   B=A.';

   B(restart:N)=B(1:N-restart+1);

   result=B.';