Install R <= 2.13 with Homebrew
Probably Homebrew has changed much since then, with Superenv and stuff. If you are stuck at an old R version and need to install it using Homebrew, you need to add depends_on :x11 to /usr/local/Library/Formula/r.rb, like so:
# /usr/local/Library/Formula/r.rb class R < Formula url 'http://cran.r-project.org/src/base/R-2/R-2.13.1.tar.gz' homepage 'http://www.r-project.org/' md5 '28dd0d68ac3a0eab93fe7035565a1c30' depends_on 'valgrind' if valgrind? depends_on :x11 # Add this line def options [ ['--with-valgrind', 'Compile an unoptimized build with support for the Valgrind debugger.'] ] end # ...