title: Python RandomForest - Unknown label Error
body: <p>I have trouble using RandomForest fit function</p>
  
  <p>This is my training set</p>
  
  <pre><code>         P1      Tp1           IrrPOA     Gz          Drz2
  0        0.0     7.7           0.0       -1.4        -0.3
  1        0.0     7.7           0.0       -1.4        -0.3
  2        ...     ...           ...        ...         ...
  3        49.4    7.5           0.0       -1.4        -0.3
  4        47.4    7.5           0.0       -1.4        -0.3
  ... (10k rows)
  </code></pre>
  
  <p>I want to predict P1 thanks to all the other variables using sklearn.ensemble RandomForest</p>
  
  <pre><code>colsRes = ['P1']
  X_train = train.drop(colsRes, axis = 1)
  Y_train = pd.DataFrame(train[colsRes])
  rf = RandomForestClassifier(n_estimators=100)
  rf.fit(X_train, Y_train)
  </code></pre>
  
  <p>Here is the error I get:</p>
  
  <pre><code>ValueError: Unknown label type: array([[  0. ],
         [  0. ],
         [  0. ],
         ..., 
         [ 49.4],
         [ 47.4],
  </code></pre>
  
  <p>I did not find anything about this label error, I use Python 3.5.
  Any advice would be a great help !</p>