[R] lattice: add vertical lines in xyplot

[baptiste auguie]

Hi list,

This is a very basic question about lattice: I wish to add some  
vertical lines in each panel of a xyplot as demonstrated in this  
example:

> library(lattice)
>
> xx <- seq(1, 10, length=100)
> x <- rep(xx, 4)
> y <- c(cos(xx), sin(xx), xx, xx^2/10)
> fact <- factor(rep(c("cos", "sin", "id", "square"), each=100))
> fact2 <- factor(rep(c("periodic", "not periodic"), each=100))
>
> my.df <- data.frame(x=x, y=y, fact = fact, fact2 = fact2)
>
> head(my.df)
>
> xyplot(y~x | fact,  data = my.df,  groups= fact2) # this plots as  
> expected
>
> my.lines <- c(5, 6) # i want to draw these vertical lines, according  
> to the level of fact2
>
> xyplot(y~x | fact,  data = my.df,  groups= fact2,
> 	panel=function(x, y,subscripts,  ...) {
> 		panel.xyplot(x, y,subscripts,  ...)
> 		 panel.abline(v=my.lines[subscripts])}
> 	)

this gives me an error, but I don't understand the help for the panel  
function.

Alternatively, I tried in ggplot but here again, I get an error:

> p <- ggplot(my.df, aes(x, y)) +
> 	geom_path(aes(colour = fact)) +
> 		facet_grid(fact2 ~ fact) +
> 		 geom_vline(intercept = my.lines) # how do I select the relevant  
> one ?
> p

Many thanks,

baptiste

_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag