title: How to manage multiple package locations (folders) in R?
body: <p>Before I upgrade to R-2.14, I want to take the opportunity to rationalise the folder structure of my installed packages.</p>
  
  <p>At the moment I use the R default, i.e. all new installed packages goes to R_LIBS_USER.  However, I really distinguish between two classes of package:</p>
  
  <ul>
  <li>Packages I use repeatedly to do my work, e.g. <code>plyr</code>, <code>data.table</code>, etc.</li>
  <li>Packages I install just to experiment with (often to replicate a question or answer on StackOverflow)</li>
  </ul>
  
  <p>Since <code>install.packages</code> offers one the option to specify a <code>lib</code> argument, this is clearly possible.</p>
  
  <p>Is there an easy way to manage package locations, e.g. by creating some sensible settings / wrapper function in <code>.RProfile</code> or <code>RProfile.Site</code>?</p>