How to set the R_HOME environment variable to the R home directory?

Question

I am trying to import rpy2 into python and I am getting this error:

RuntimeError: The R home directory could not be determined.
Try to install R <https://www.r-project.org/>,
set the R_HOME environment variable to the R home directory, or
add the directory of the R interpreter to the PATH environment variable.

I am completely lost here as I have no idea what this is telling me. I tried to search up how to set the environment variable and couldn't find anything detailed enough that was helpful for me. I would appreciate it if the answer could be very straightforward as I am just a newbie. I am running OSX 10.11.

Thank you (my first post, I apologize if I overlooked any rules in posting)

Answer 1

It is the other way around -- the R in your PATH should know its home:

edd@don:~$ R RHOME
/usr/lib/R
edd@don:~$ 

This echos the last line recommendation -- have your R in the PATH.

On another machine with both R and R-devel, I choose to address the latter under a different name. Still, each knows its HOME:

edd@max:~$ /usr/local/lib/R-devel/bin/R RHOME
/usr/local/lib/R-devel/lib/R
edd@max:~$ R RHOME
/usr/lib/R
edd@max:~$ 

Answer 2

Setting R_HOME this way worked for me

import os
os.environ['R_HOME'] = '/path/to/R'