[R-SIG-Mac] Rgraphviz installation problem

[Seth Falcon]

I'm going to try and summarize, but I can't easily test this, so I
would appreciate it others could confirm, etc.

To install Rgraphviz on OSX when using the binary installation of R
downloaded from CRAN (that is, the R app), do the following:

1. Install the _graphviz_ binary from http://r.research.att.com/.

2. Install the _binary_ version of the BioC Rgraphviz package:

     source("http://bioconductor.org/biocLite.R")
     biocLite("Rgraphviz")