title: What to do when a package is not available for our R version?
body: <p>Very often, when I try to download a package, I've got the following message : </p>
  
  <pre><code>Warning in install.packages :
    package ‘XXXX’ is not available (for R version 3.0.1)
  </code></pre>
  
  <p>Is it not possible to simulate an old version of R to use the package ? </p>