Custom hombrew r formula. Tcl-tk support is added using the Mac OS system tcl-tk framework (see r.rb formula lines 60-62).
Operational X11/Xquartz and Mac OS Command Line Tools installations are build requirements. X11/Xquartz is required because the tk.h header file used in base r tcltk package includes X11 headers. Mac OS Command Line Tools must be installed for the appropriate Tcl-tk config files to be available.
Additional compile options are available.