title: Use ls() or objects() to get objects of class data.frame
body: <p>Is there anyway I can loop through some set of objects and apply a function to each?</p>
  <p>When I type <code>ls()</code> or <code>objects()</code>, it returns a list of object names. I could like to iterate through this list, identify those which are <code>data.frame</code>, and then run a function against each object.</p>
  <p>How do I pass an entry from <code>ls</code> or <code>objects</code> through a function?</p>