title: ValueError: Unknown label type: array while using Decision Tree Classifier and using a custom dataset
body: <p>Given below is my code</p>
  
  <pre><code>dataset = np.genfromtxt('train_py.csv', dtype=float, delimiter=",")
  X_train, X_test, y_train, y_test = train_test_split(dataset[:,:-1],dataset[:,-1], test_size=0.2,random_state=0)
  model = tree.DecisionTreeClassifier(criterion='gini')
  #y_train = y_train.tolist()
  #X_train = X_train.tolist()
  model.fit(X_train, y_train)
  model.score(X_train, y_train)
  predicted= model.predict(x_test)
  </code></pre>
  
  <p>I am trying to use the decision Tree classifier on a custom dataset imported using the numpy library. But I get a ValueError which is given below when I try to fit the model.I tried using both numpy arrays and non numpy arrays such as lists but still dont seem to figure out what is causing the error. Any help appreciated. </p>
  
  <pre><code>    Traceback (most recent call last):
    File "tree.py", line 19, in &lt;module&gt;
      model.fit(X_train, y_train)
    File "/usr/local/lib/python2.7/dist-packages/sklearn/tree/tree.py", line 177, in fit
      check_classification_targets(y)
    File "/usr/local/lib/python2.7/dist-packages/sklearn/utils/multiclass.py", line 173, in check_classification_targets
      raise ValueError("Unknown label type: %r" % y)
  
  ValueError: Unknown label type: array([[ 252.3352],....&lt;until end of array&gt;
  </code></pre>