MATLAB® / R Reference, by David Hiebeler
Here is the current version of my MATLAB / R Reference in PDF form (last updated July 14, 2011). I wrote the initial version of this during Spring 2007, as I learned R while teaching my Modeling and Simulation course (I'd previously used only MATLAB for prior versions of the course). I have since continued to add to it. The reference is ideally suited for someone who is good in one package, and is trying to read code in or learn the other. It may also be useful as a reference (not a tutorial) for someone learning one of the packages, even with no experience in the other.
Note: It has been some time since I last updated the document, but I haven't abandoned it. I have a pretty good list of updates I need to merge in. I hope to release an updated version hopefully by the end of 2013.
Here is a record of the various changes made to the document over time.