RogBlog

I love Sweave for writing LaTeX documents with embedded R code, and R’s cacheSweave package helps tremendously in avoiding repetition of time-consuming computations.  (Thank you, Roger Peng, for writing cacheSweave!)  One catch that is evident from a careful perusal of the cacheSweave vignette but which I keep forgetting is that cacheSweave will not cache R code chunks with side effects! Side effects include (but are not limited to):

• print() and related display-to-screen commands
• plot() and other graphical-output commands

This failure to cache is silent, so it can be confusing; I keep on forgetting about it.  So this post is as much as anything else a note to myself to remember.  The simple solution is to separate out the long-computation chunks from the side-effect chunks and cache only the former (see the vignette for details).