QR with columns pivoting

Is there any sample matlab code computing QR decomposition with columns pivoting for a matrix?

I do not need an internal function, I would like to know the method...

Thanks for your help...

[Newlearner]

Hello, I am trying to find a set of indices J, containing the r column pivots of a matrix using CPQR, how can I do that? Thanks

[Christine Tobler]

In practice, call

[~, ~, J] = qr(A, 'econ', 'vector')

To find the underlying algorithm as was the original question, see the reference LAPACK implemementation (Fortran code) for dlaqp2 (this doesn't have some of the optimizations in dlaqp3, but is easier to read).