title: R, install package from source vs. use install.package() and CRAN mirror
body: <p>The answers to this question: <a href="https://stackoverflow.com/questions/43297797/determine-if-r-package-is-available-on-linux">Determine if R package is available on Linux</a> mention installing R packages from source, specifically in the context of R running on linux.  For instance, pages such as <a href="https://cran.r-project.org/bin/linux/debian/" rel="nofollow noreferrer">this</a> and <a href="https://cran.r-project.org/bin/linux/ubuntu/" rel="nofollow noreferrer">this</a> give specific instructions for installing packages on various linux systems, and StackOverflow questions such as: <a href="https://stackoverflow.com/questions/1474081/how-do-i-install-an-r-package-from-source">How do I install an R package from source?</a> address the issue more generally.  Finally, the answer in <a href="https://stackoverflow.com/a/43298332/3541976">this</a> SO question mentions that unix users tend to install packages from source.</p>
  
  <p>I've used R on my university's CentOS linux server a decent bit and have always just added new packages using <code>install.packages()</code> from within R and specifying a CRAN repository.  This generally works fine, though I do notice that it often takes far longer than when installing packages on my personal computer.</p>
  
  <p>What would be the reason to:</p>
  
  <p>(a) Download the .tar.gz file and specify its path via the <code>path</code> argument in <code>install.packages()</code> and/or</p>
  
  <p>(b) Install the package directly from a command line call, as specified, for instance, <a href="https://cran.r-project.org/bin/linux/debian/" rel="nofollow noreferrer">here</a>, <a href="https://cran.r-project.org/bin/linux/ubuntu/" rel="nofollow noreferrer">here</a>, and <a href="https://stackoverflow.com/a/43298332/3541976">here</a></p>
  
  <p>as opposed to just using <code>install.package()</code> from within R and specifying a given online repository?</p>