title: Weka output of attribute selection
body: <p>I'm using weka to select attributes from my dataset, but I don't understand one thing: for example, I have this output after attributes selection with InfoGainAttributeEval + Ranker</p>
  
  <pre><code>Ranked attributes:
   0.354       1 attr12
   0.333      46 attr4
   0.316      75 attr7
   0.304      96 attr1
  </code></pre>
  
  <p>Well, I know the first value is the information gain, but what does it means "1 attr12"? What's that number "1"?
  Thanks</p>