LAMMPS library: Gather specific atoms and insert small molecules

Dear LAMMPS users,

I'm following up on the old post on the list.
Trying to get all coordinates for a given
type, e.g. 2, I put this in my LAMMPS script:

group MYGRP type 2
variable MYCOORDS atom x
variable MYCOUNT equal count(MYGRP)

Using the functions from library.cpp by

double* pnatoms = (double*) lammps_extract_variable(lmp, "MYCOUNT", NULL);
                        int natoms = (int)(*pnatoms);
                                           double* coords = (double*)
lammps_extract_variable(lmp, "MYCOORDS", "MYGRP");

However, coords contains only zeros, e.g. 0.0, 0.0, 0.0.
Apparently I'm doing something wrong, but I'm not sure what.

Maybe somebody can point me in the right direction.

Best regards,