Since our package may be probably taken as an example if ineffcient coding any improvement is more than welcome :-). Yes of course, go ahead Artur, thanks Stefano -- ________________________________________________________________________ Stefano Fachin Professore Ordinario di Statistica Economica Dip. di Scienze Statistiche "Sapienza" Università di Roma P.le A. Moro 5 - 00185 Roma - Italia Tel. +39-06-49910834 fax +39-06-49910072 web http://stefanofachin.site.uniroma1.it/