I don't think the code below does what's requested, as it assumes a single overall fit for all panels, and I think the requester wanted separate fits by panel. This can be easily done, of course, by a minor modification:
xyplot( y ~ x | z, panel = function(x,y,...){ panel.xyplot(x,y,...) panel.abline(lm(y~x),col="blue",lwd=2) panel.abline(rlm(y~x),col = "red",lwd=2) }) Note that the coefficients do not need to be explicitly extracted by coef(), as panel.abline will do this automatically. Bert Gunter Genentech Nonclinical Statistics South San Francisco, CA 94404 650-467-7374 Alan S Barnett wrote: > How do I add to a trellis plot the best fit line from a robust fit? I > can use panel.lm to add a least squares fit, but there is no panel.rlm > function. How about using panel.abline() instead of panel.lmline()? fit1 <- coef(lm(stack.loss ~ Air.Flow, data = stackloss)) fit2 <- coef(rlm(stack.loss ~ Air.Flow, data = stackloss)) xyplot(stack.loss ~ Air.Flow, data=stackloss, panel = function(x, y, ...){ panel.xyplot(x, y, ...) panel.abline(fit1, type="l", col="blue") panel.abline(fit2, type="l", col="red") }, aspect=1) -- Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 512-0171 (M, W, F) fax: (917) 438-0894 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.