R devel - Jun 2003 - lattice and Sweave

I'm having trouble using lattice and Sweave together.

An example of the trouble is the chunk

<<fig=true, eps=false>>library(nlme)
data(Orthodont)
plot(Orthodont)
@

This gives a warning

Warning message:
No Active Device, using default values in: trellis.par.get("add.text")

 and creates a pdf file with no pages.

I think this is related to the fact that a figure chunk is evaluated
twice, once with no device open.  Possibly related anomalies include the
fact that you end up with a theme set for the null
device:
> names(lattice.theme)
[1] "null device" "postscript"  "pdf"
which doesn't look right.

The chunk
<<>>library(lattice)

 data(airquality)
 windspeed<-equal.count(airquality$Wind, 4)
 temperature<-equal.count(airquality$Temp, 4)

 print(xyplot(Ozone~Solar.R|windspeed*temperature, data=airquality,
col="darkred"))
@

works fine, so I think the problem is related to using trellis.par.get
before setting a trellis device.


	-thomas

Thomas Lumley <tlumley@u.washington.edu> writes:
> I'm having trouble using lattice and Sweave together.
> 
> An example of the trouble is the chunk
> 
> <<fig=true, eps=false>>> library(nlme)
> data(Orthodont)
> plot(Orthodont)
> @
I have a big sign next to my monitor saying 

 When using Sweave you _must_ print a lattice plot.

because I have made this mistake so many times.  In my rush to finish
the slides for a short course that I am teaching today and tomorrow I
forgot this and contacted Deepayan, who is travelling in India right
now, in a panic. He calmly told me "you forgot to print".

It will work if you use

 print(plot(Orthodont))