title: Error : "sh: gfortran: command not found" | Ubuntu 16.04
body: <p>I am trying to install package , <code>circular</code>, I get the below error during the installation.</p>
  <p><img src="https://i.stack.imgur.com/EMrXv.png" alt="enter image description here" /></p>
  <p>I tried a few option that were suggested in a few posts but it didn't work. I also tried loading other packages such as <code>spatstat</code> and this error doesn't occur while doing that.</p>
  <p>Could anyone please assist me in resolving this issue.</p>