title: How to install R packages via proxy [user + password]
body: <p>I need authentication to use internet, say these are my variables:</p>
  
  <ol>
  <li>Proxy : 1ncproxy1</li>
  <li>Port : 80</li>
  <li>Loggin : MyLoGiN</li>
  <li>Pass : MyPaSs</li>
  </ol>
  
  <p><strong>How can I install a package in R and its addon packages ?</strong>
  Such that the following would work:</p>
  
  <pre><code>install.packages("TSA", dependencies=TRUE)
  </code></pre>
  
  <p>Without our having internet connection failutes? </p>
  
  <p>I tried this:</p>
  
  <pre><code>Sys.setenv("ftp_proxy" = "1ncproxy1","ftp_proxy_user"="MyLoGiN","ftp_proxy_password"="MyPaSs")#Port = 80
  </code></pre>
  
  <p>ButI get :</p>
  
  <pre><code>Warning: unable to access index for repository http://cran.ma.imperial.ac.uk/src/contrib
  # or 
  cannot open: HTTP status was '407 Proxy Authentication Required'
  </code></pre>
  
  <p>Many thanks,</p>