Actually, I 'm using "mgcv" package. But I learnt basic linear regression in my school, it is really hard for me to handle these problem! by the way, i need to work harder! -- View this message in context: http://r.789695.n4.nabble.com/About-GAM-in-R-Need-YOUR-HELP-tp3610522p3611796.html Sent from the R help mailing list archive at Nabble.com.