[eigen] initializing a matrix so that all columns are copies of one column

[Douglas Bates <bates@xxxxxxxxxxxxx>]

In an optimization algorithm I have an n by n+1 matrix whose columns
correspond to parameter vectors.  At one point I want to subtract a
given n vector from each column, convert to absolute values, and find
the maximum coefficient in each row.  The matrix is called pts and the
position I want to subtract is a centroid called c.  If I can think of
a way of creating another n by n+1 matrix whose columns are copies of
c, let's call it cmat, then I can write

  VectorXd maxdev( (pts - cmat).array().abs().rowwise().maxCoeff() );

but the best I have been able to come up with for constructing cmat is

  MatrixXd  cmat(n, n+1);
  for (int i = 0; i <= n; ++i) cmat.col(i) = c;

Is there a more elegant way of doing this?