Hello there, I just compiled gretl-1.9.12 on Linux with extra gcc compile flag -Wlogical-op It said ../lib/src/gretl_func.c:5770:3: warning: logical 'or' of collectively exhaustive tests is always true [-Wlogical-op] Source code is     if (dreq == FN_NEEDS_QM &&     (!dataset_is_time_series(dset) ||      (dset->pd != 4 || dset->pd != 12))) {     gretl_errmsg_set("This function needs quarterly or monthly data");     return 1;     } On the third lane, suggest swap || for &&. Regards David Binderman