Installing rpy2 on MacOS
If using a Miniconda environment this works:
conda install -c r rpy2
Found the solution in this thread.
env CC=/usr/local/Cellar/gcc/X.x.x/bin/gcc-X pip install rpy2
Running the above command by replacing the gcc version with the latest version on your machine should solve the problem. For example, on my mac, I ran
env CC=/usr/local/Cellar/gcc/8.2.0/bin/gcc-8 pip install rpy2