Sweave is combined LaTeX and S code. For more information on Sweave:
The highlighting file depends on the syntax highlighting files for LaTeX and R Script, and a big part was borrowed from the LaTeX syntax highlighting file.
This is work in progress - feedback is highly welcome.
Update 2014-06-19: Note that this is abandonware. Please use the revised version at http://kde-files.org/content/show.php?content=165676