The actual Sweave file is in pmc_tutorial/knit_pmc_tutorial.Rnw, and is compiled by the Makefile in that directory using the knitr tools.  knitr is a remake of Sweave that handles caching, syntax highlighting, formating, and alternative input and output types more naturally. The pmc_tutorial.Rnw file included here is produced by knitr using knit_pmc_tutorial.Rnw, and is essentially a .tex file consistent with the built-in Sweave.  
