title: What is Class Index in WEKA?
body: <p>I have to use WEKA in my java code for prediction. Basically I have to study a given code and reuse it. </p>
  
  <p><code>testdata.setClassIndex(data.numAttributes() - 1);</code></p>
  
  <p>I am unable to understand what the above line means.
  What is a Class Index?</p>
  
  <p><code>testdata</code> and <code>data</code> are  Intances object.</p>