title: mdrr dataset in caret package
body: <p>The <code>mdrr</code> dataset in <code>caret</code> package is a set of two objects; data.frame (<code>mdrrDescr</code>), and an ordinary factor (<code>mdrrClass</code>). when I try to run <code>View()</code> command for <code>mdrrClass</code> it shows a factor with zero entries. why is it like this? also how to create a factor like that ? I think it'll be better to understand the question if you just run these commands.</p>
  
  <pre><code>data(mdrr)
  class(mdrrClass)
  View(mdrrClass)
  </code></pre>
  
  <p>it says: </p>
  
  <blockquote>
    <p>"Showing 1 to 0 of 528 entries"</p>
  </blockquote>
  
  <p>on the source pane.</p>