title: ggplot function not found in jupyter notebook with rpy2
body: <p>I am working on a computer cluster and testing out how to use a Jupyter notebook on it. I encountered this problem while trying to use ggplot2. I've tried installing the package in the notebook, with R in the command line, and with conda install, and r-ggplot2 (version 2.2.1) shows up in conda packages. Any ideas?</p>
  
  <p><img src="https://i.stack.imgur.com/55UYI.png" alt="The error I got on the notebook is here"></p>