cov = covariance_matrix_init (n_all_vars, all_vars, ONE_PASS, PAIRWISE, MV_ANY);
reader = casereader_create_counter (reader, &row, -1);
cov = covariance_matrix_init (n_all_vars, all_vars, ONE_PASS, PAIRWISE, MV_ANY);
reader = casereader_create_counter (reader, &row, -1);