title: Cross_val_predict in SKLearn - expected an array but
body: <p>I have a very simple pandas DataFrame (X), with eight columns, and twenty rows full of floats. Then, I have another DataFrame (y), that is twenty rows. When I run:</p>
  
  <pre><code>score = cross_val_score(clf, X, y, scoring='accuracy')
  </code></pre>
  
  <p>I get no error and the results make sense (there is nothing wrong with the DataFrame, basically). However, when I run:</p>
  
  <pre><code>predicted = cross_val_predict(clf, X)
  </code></pre>
  
  <p>or</p>
  
  <pre><code>predicted = cross_val_predict(clf, X.values)
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>Expected array-like (array or non-string sequence), got None
  </code></pre>
  
  <p>Any suggestions as to what the problem might be?</p>