'copies all columns of source into some columns of self.
<indices> must be a row vector. Its elements are float32\'s representing
integers, e.g. "34.0" means the integer "34". after this call, for all
r,c, self[r,indices[c]]=source[r,c]. This returns self.
Negative indices are interpreted in the usual Python way: all elements
of <indices> had better be in the range [-self.shape[1], self.shape[1]-1].
This does bounds checking, but out of bounds indices do not raise an
exception (because the programmer was lazy). Instead, they result in NaN
values in <self>.'

def set_selected_columns(self, indices, source):

    err_code = _eigenmat.setSelectedRows(self.p_mat, source.p_mat, indices.p_mat)
    if err_code:
        raise generate_exception(err_code)
    return self
