title: How is to add R and Rtools paths in the environment variable?
body: <p>I have installed <code>R-3.5.1</code> and <code>Rtools35.exe</code>. But I am unable to install packages in <code>R</code>. Somewhere I got,</p>
  <blockquote>
  <p>Make sure the R and Rtools paths are added in the environment variable.</p>
  </blockquote>
  <p>But I don't know what is environment variable and how is to add  R and Rtools paths in the environment variable?</p>
  <h3>Edit</h3>
  <p>The answer provided <a href="https://stackoverflow.com/questions/47539125/how-to-add-rtools-bin-to-the-system-path-in-r">How to add Rtools\bin to the system path in R</a> requires <code>library(devtools)</code>. But <code>install.packages(&quot;devtools&quot;)</code> isn't working.</p>