What about using geom_vline and geom_hline to draw borders. I just couldn't find the way to set the intercept max value for geom_vline and hardcoded it to 5.5
d<- ggplot(mtcars, aes(x=mpg, y=wt)) + geom_point() + facet_grid(. ~ cyl)+ scale_y_continuous(limits=c(0,NA))+ scale_x_continuous(limits=c(0,NA)) mtcars2<-data.frame((mtcars),intercept=0) dd<- d + geom_hline(data=mtcars2,colour="red",size=3)+ geom_vline(data=mtcars2,colour="red",size=3) mtcars3<-data.frame((mtcars),intercept=5.5) ddd <- dd + geom_hline(data=mtcars3,colour="red",size=3) ddd > > Hi > > > > I want to highlight two panels in a grid created > with facet_grid() by > > putting a box around it or usiong another > background colour. Is this > > possible, and if yes, how? > > It's possible, but not particularly easy. You could > do something like: > > # Background colours > background <- data.frame( > cyl = c(4, 6, 8), > fill = c(NA, alpha("red", 0.2), alpha("black", > 0.3)) > ) > > # Points defining square region for background > square <- with(mtcars, data.frame( > x = c(min(mpg), max(mpg), max(mpg), min(mpg)), > y = c(min(wt), min(wt), max(wt), max(wt)) > )) > > ggplot(mtcars, aes(x=mpg, y=wt)) + > geom_polygon(aes(x=x,y=y, fill=fill), > data=merge(background, square)) + > geom_point() + > scale_fill_identity() + > facet_grid(. ~ cyl) > > Hadley > > -- > http://had.co.nz/ > > ______________________________________________ > 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. > Felipe D. Carrillo Fishery Biologist US Fish & Wildlife Service California, USA ____________________________________________________________________________________ Be a better friend, newshound, and ______________________________________________ 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.