" Must one compose a panel function?" Depending on what you want exactly, no. Add the argument
type="g" to your call. (e.g. densityplot(~fallrates, groups = prepost,type="g",... ) See ?panel.xyplot and recall that lattice passes down arguments that it does not know what to do with to the panel function. Bert Gunter Genentech Nonclinical Biostatistics -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Giles Sent: Thursday, April 22, 2010 1:31 PM To: r-help@r-project.org Subject: [R] How to insert gridlines in lattice density plot Greetings. How can I insert gridlines in the following density plot call? Must one compose a panel function? 'data.frame': 46 obs. of 2 variables: $ fallrates: num 5.2 7.1 7.1 9.8 3.7 7.5 5 6.2 1.5 2.9 ... $ prepost : Factor w/ 2 levels "post","pre": 2 2 2 2 2 2 2 2 2 2 ... library(lattice) densityplot(~fallrates, groups = prepost, kernal="triangular", lwd=2, plot.points = TRUE, ref = TRUE, auto.key = list(columns = 2), main="Estimated fall rate density, pre and post intevention") Thank you for your consideration and comments. Giles Crane ______________________________________________ R-help@r-project.org 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@r-project.org 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.