Flip matrix by every nth row

I have a 121x14 matrix. I want to flip the first 11 rows vertically and repeat so on for the rest of the matrix. I know it is possible to flip an entire matrix using:

flipup(name)

Answer 1

[Stephen23]

This is MATLAB, so just generate the indices:

 idx = reshape(flipud(reshape(1:121,11,11)),1,121);
 mat(idx,:)

These indices only need to be generated once, and can be used multiple times.