title: Error in readRDS(file) : unknown input format
body: <p>I am trying to install custom packages in my Rprofile.site file. I want to install packages in the site file because I have to install these packages on several users' computers. However, I am getting the following the error whenever I launch R. </p>
  
  <pre><code>Error in readRDS(file) : unknown input format
  </code></pre>
  
  <p>I have the following code added to the end of my Rprofile.site file. </p>
  
  <pre><code>if(length(grep("customPackage", installed.packages()))==0) {
      install.packages("customPackage", repos=NULL, type="source")
  }
  </code></pre>
  
  <p>The error keeps repeating itself as well until I stop the R session. If I remove that code from the site file and just install the package directly in an R session though it works fine. </p>
  
  <p>The only reason I want to do it in the site file is because I will keep adding more custom packages that need to be installed on each user's machine and I would rather just call it from the site file than have each user install each custom package once. </p>
  
  <p>I tried searching for the error and got a variety of answers which spoke about deleting the .Rhistory file (which I tried, but didn't work), or installing the latest version of R (I am on R-2.15.0 which is the latest version so that won't help either). I was wondering if there was any other solution to fixing this problem. </p>