title: How to use the actual feature names instead of "X" in scikit-learn DecisionTreeRegressor?
body: <p>I suppose this is possible since in the def of <code>fit</code> function <a href="http://scikit-learn.org/stable/modules/generated/sklearn.tree.DecisionTreeRegressor.html#sklearn.tree.DecisionTreeRegressor.fit" rel="noreferrer">it says</a>:</p>
  
  <blockquote>
    <p>X : array-like, shape = [n_samples, n_features]</p>
  </blockquote>
  
  <p>Now I have,</p>
  
  <p><img src="https://i.stack.imgur.com/ap0ns.png" alt="enter image description here"></p>
  
  <p>I can certainly generate a string representation of the decision tree then replace <code>X[]</code> with actual feature names. But I wonder if the <code>fit</code> function could directly take feature names as part of inputs? I tried the following format for each sample</p>
  
  <ul>
  <li><p>[1, 2, "feature_1", "feature_2"]</p></li>
  <li><p>[[1, 2], ["feature_1", "feature_2"]]</p></li>
  </ul>
  
  <p>but neither worked. What does that <code>shape</code> mean? Could you please give me an example?</p>