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

This is horribly hacky and probably belies my limited UNIX shell fu, but it works for me on a Fedora 17 box with the pdfjam package installed (not an R package, but from the YUM repos)

pdf("pdf1.pdf")
plot(1:10)
dev.off()

pdf("| pdfjoin --outfile \"pdf2.pdf\" && pdfjoin pdf1.pdf pdf2.pdf --outfile pdf1.pdf && rm pdf2.pdf")
plot(10:1)
dev.off()

The output in R is:

> pdf("| pdfjoin --outfile \"pdf2.pdf\" && pdfjoin pdf1.pdf pdf2.pdf --outfile pdf1.pdf && rm pdf2.pdf")## && pdfunite joined.pdf tmp.pdf joined.pdf && rm tmp.pdf")
> plot(10:1)
> dev.off()
          ----
  pdfjam: This is pdfjam version 2.08.
  pdfjam: Reading any site-wide or user-specific defaults...
          (none found)
  pdfjam: No PDF/JPG/PNG source specified: input is from stdin.
  pdfjam: Effective call for this run of pdfjam:
          /usr/bin/pdfjam --fitpaper 'true' --rotateoversize 'true' --suffix joined --outfile pdf2.pdf -- /dev/stdin - 
  pdfjam: Calling pdflatex...
  pdfjam: Finished.  Output was to 'pdf2.pdf'.
          ----
  pdfjam: This is pdfjam version 2.08.
  pdfjam: Reading any site-wide or user-specific defaults...
          (none found)
  pdfjam: Effective call for this run of pdfjam:
          /usr/bin/pdfjam --fitpaper 'true' --rotateoversize 'true' --suffix joined --outfile pdf1.pdf -- pdf1.pdf - pdf2.pdf - 
  pdfjam: Calling pdflatex...
  pdfjam: Finished.  Output was to 'pdf1.pdf'.
null device 
          1

Basically, pdfjoin will take input from stdin if it is the only input file so I pipe the output from pdf() to the pdfjoin program and specify the output file using the --outfile argument. Then using && is join the original pdf1.pdf with the pdf2.pdf just created, specifying that the output PDF is pdf1.pdf, the name of the original PDF.