Make Sweave or knitr put graphics suffix in `\includegraphics{}`

Question

I just run into the (curious) problem that when submitting a (pdf)LaTeX manuscript to some Elsevier journal the filenames of figures needed to be complete in order to found by their pdf building and checking syste, i.e.:

\includegraphics{picture.pdf}

Is there any easy and convenient way to tell Sweave or knitr to do that?

Edit:

• I'm familiar with sweave's include=FALSE option
• I also feel quite capable to patch utils:::RweaveLatexRuncode

However, for the moment I'm hoping that there's something more convenient and elegant.

It's also about handing out the .Rnw files as supplementary material or vignettes. From a didactic point of view I don't like these tweaks that make the source code much more complicated for the new users of whom I hope they read it.

(Which is also why I really appreciate the recently introduced print=TRUE in Sweave)

Answer 1

You can modify the plot hook a little bit in knitr to add the file extension:

<<>>=
knit_hooks$set(plot = function(x, options) {
  x = paste(x, collapse = '.') # x is file.ext now instead of c(file, ext)
  paste0('\\end{kframe}', hook_plot_tex(x, options), '\\begin{kframe}')
})
@

See 033-file-extension.Rnw for a complete example. To understand what is going on behind the scene, see the source code of the default LaTeX hooks in knitr.

Answer 2

A brute force solution is to explicitly create the files yourself in the R snippet. Set the option for graphics etc to false but have the code evaluated so that the file is created, and then have latex call them with the very \includegraphics{} call you show.

I used similar schemes for simple caching: if the target file exists, skip the code creating.