I'm new to Eigen and trying to port some existing python code to C++.

I have a matrix and want to keep only those row/columns where the diagonal term is larger than 0.

I managed to get an array of bool with the positive diagonal positions,

VectorXd Diag = M.diagonal();
Array<bool, Dynamic, 1> iPos = Array<bool, Dynamic, 1>(n);
iPos = (Diag.array() > 0);

However slicing seems not to be possible with an array of booleans, so I either need to convert to an array of int (but how?) or I need to do this differently alltogether.

Any advice?