title: imblearn.oversampling SMOTENC ValueError
body: <p>This is my first time using SMOTENC to upsampling my categorical data. However, I've been getting error. Can you please advice what should I pass for categorical_features in SMOTENC? </p>
  
  <pre><code>from imblearn.over_sampling import SMOTENC
  
  x=df.drop("A",1)
  y=df["A"]
  
  smote_nc = SMOTENC(categorical_features=['A','B','C','D','E','F','G','H'], random_state=0)
  X_resampled, y_resampled = smote_nc.fit_resample(x, y)
  </code></pre>
  
  <p>ERROR: </p>
  
  <pre><code>---------------------------------------------------------------------------
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-26-f6c9d8a17967&gt; in &lt;module&gt;
  
  ---&gt; 14 X_resampled, y_resampled = smote_nc.fit_resample(x, y)
       15 #sm = SMOTE(random_state=100)
       16 #ros = RandomOverSampler()
  
  ~/.local/lib/python3.5/site-packages/imblearn/base.py in fit_resample(self, X, y)
       82             self.sampling_strategy, y, self._sampling_type)
       83 
  ---&gt; 84         output = self._fit_resample(X, y)
       85 
       86         if binarize_y:
  
  ~/.local/lib/python3.5/site-packages/imblearn/over_sampling/_smote.py in _fit_resample(self, X, y)
      986     def _fit_resample(self, X, y):
      987         self.n_features_ = X.shape[1]
  --&gt; 988         self._validate_estimator()
      989 
      990         # compute the median of the standard deviation of the minority class
  
  ~/.local/lib/python3.5/site-packages/imblearn/over_sampling/_smote.py in _validate_estimator(self)
      979                 raise ValueError(
      980                     'Some of the categorical indices are out of range. Indices'
  --&gt; 981                     ' should be between 0 and {}'.format(self.n_features_))
      982             self.categorical_features_ = categorical_features
      983         self.continuous_features_ = np.setdiff1d(np.arange(self.n_features_),
  
  ValueError: Some of the categorical indices are out of range. Indices should be between 0 and 7
  </code></pre>