[R] Sweave with pdf(): how to remove mention "null device"

[Matthieu Stigler]

Hi

I am sorry, my question seems simple and must already have been asked, 
but I did not find any aswser on the archives :-(

I am trying to use a plot in Sweave, where I include myself the statement
<<results=tex,echo=FALSE>>=
pdf("plot.pdf")
  plot(runif(100))
dev.off()
cat("\\includegraphics{plot}\n\n")

@

as is documented in the Sweave user guide A.9. The problem is that a 
"null device 0" is printed in my document! Indeed, each time one opens 
pdf() or any device, some mention "pdf" inevitably shows up... try:

pdf()
plot(runif())
dev.off()

How can one get rid of this? The only workaround I found is to place it 
into a if() loop:

for(i in 1:1){
pdf()
plot(runif())
dev.off()
}

so there is no track of the mention null device, and my sweave pdf looks 
better. Any idea of a more elegant solution?

Thanks!!