def elimination_matrix(n):
 vech_indices = vec(np.tril(np.ones((n, n))))
 return np.eye((n * n))[(vech_indices != 0)]

def elimination_matrix ( n ) : vech_indices = vec ( np . tril ( np . ones ( ( n , n ) ) ) ) return np . eye ( ( n * n ) ) [ ( vech_indices != 0 ) ]
create the elimination matrix l_n which satisfies vech(m) = l_n vec(m) for any matrix m parameters returns .