Dear experts I need to fit a model with nested random effects (cow within herd and season), and I’m not sure how to do it with R. Using LME I know how to fit: cow within herd fit4 <- lme(milk ~ days + season + season*days , data=xxx, random = ~1 + days| herd/cow) How I can fit: cow within herd and season? In SAS I would write it: Proc mixed data=xxx; Class herd cow season; Model milk= days season days*season; Random intercept days/type=cs subject = cow(herd season) ; Thank for your help Maria _________________________________________________________________ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-us&source=wlmailtagline [[alternative HTML version deleted]]