% brew install R
Unsatisfied dependency: XQuartz
Homebrew does not package XQuartz. Installers may be found at:
  https://xquartz.macosforge.org
Error: An unsatisfied requirement failed this build.

% brew install R
Error: This formula requires a fortran compiler, but we could not find one by
looking at the FC environment variable or searching your PATH for `gfortran`.
Please take one of the following actions:

  - Decide to use the build of gfortran 4.2.x provided by Homebrew using
        `brew install gfortran`

  - Choose another Fortran compiler by setting the FC environment variable:
        export FC=/path/to/some/fortran/compiler
    Using an alternative compiler may produce more efficient code, but we will
    not be able to provide support for build errors.

% brew install gfortran

% brew install R

% brew tap homebrew/science