title: How to rename the fields in a relation
body: <p>Consider the following code :</p>
  
  <pre><code>ebook = LOAD '$ebook' USING PigStorage AS (line:chararray);
  ranked = RANK ebook;
  </code></pre>
  
  <p>The relation <code>ranked</code> has two fields : the line number and the text. The text is called <code>line</code> and can be referred to by this alias, but the line number generated by <code>RANK</code> has none. As a consequence, the only way I can refer to it is as <code>$0</code>. </p>
  
  <p>How can I give <code>$0</code> an name, so that I can refer to it more easily once it's been joined to another data set and is no longer <code>$0</code>?</p>