If you use Sweave and vim, you might have wondered if it’s possible to have it syntax highlight Rnw/Snw files properly : the latex bits with LaTeX syntax and the noweb R chunks with R syntax. It is! Take a look a the screenshot below:

Screenshoot of a syntax-highlighted Sweave file

In order to have this working, you only need to properly configure your vim. First, edit your ~/.vim/filetype.vim, adding the following lines to it:

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augroup filetypedetect
  au! BufRead,BufNewFile *.r         setfiletype r
  au! BufRead,BufNewFile *.R         setfiletype r
  au! BufRead,BufNewFile *.Rnw       setf noweb
augroup END

Then, create a file named ~/.vim/after/syntax/noweb.vim, (create the directories with mkdir, if needed), with the following content:

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runtime! syntax/tex.vim
unlet b:current_syntax
 
syntax include @nowebR syntax/r.vim
syntax region nowebChunk start="^<<.*>>=" end="^@" contains=@nowebR
syntax region Sexpr  start="\\Sexpr{"  end="}" keepend
hi Sexpr gui=bold guifg=chocolate2
 
let b:current_syntax="noweb"

For users of Windows (contributed by Gabor Grothendieck)

If you’re running vim under Windows, the directory structure might difer somewhat from the above. On Windows (assuming gvim 6.3), the %VIM%\gvim63 directory should contain:

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vim.exe
gvim.exe
filetype.vim
syntax\noweb.vim

You should just do the alterations indicated above but you should save the files according to this structure.

That’s it, next time you open a file with extension .Rnw, vim will properly syntax highlight it.