How to append a plot to an existing pdf file

Question

I want to append a plot to an existing pdf long after dev.off() has been called*. After reading the pdf() help file and after reading the Q &

Answer 1

If you are willing to install the small, free, platform-independent pdftk utililty, you could use a system call from R to have it stitch all of your figures together:

## A couple of example pdf docs
pdf("Append to me.1.pdf")
plot(1:10,10:1)
dev.off()

pdf("Append to me.2.pdf")
plot(1:10,rep(5,10)) 
dev.off()

## Collect the names of the figures to be glued together
ff <- dir(pattern="Append to me")
## The name of the pdf doc that will contain all the figures
outFileName <- "AllFigs.pdf"

## Make a system call to pdftk
system2(command = "pdftk",
        args = c(shQuote(ff), "cat output", shQuote(outFileName)))

## The command above is equiv. to typing the following at the system command line
## pdftk "Append to me.1.pdf" "Append to me.2.pdf" cat output "AllFigs.pdf"