Lorenzo, I think your question was already answered by Jan van der Laan - http://r.789695.n4.nabble.com/Plotrix-Trick-tp2265893p2266722.html -- View this message in context: http://r.789695.n4.nabble.com/Plotrix-Trick-tp2267177p2267225.html Sent from the R help mailing list archive at Nabble.com.