title: TypeError: cannot perform reduce with flexible type
body: <p>I have been using the scikit-learn library. I'm trying to use the Gaussian Naive Bayes Module under the scikit-learn library but I'm running into the following error. TypeError: cannot perform reduce with flexible type</p>
  
  <p>Below is the code snippet. </p>
  
  <pre><code>training = GaussianNB()
  training = training.fit(trainData, target)
  prediction = training.predict(testData)
  </code></pre>
  
  <p>This is target</p>
  
  <pre><code>['ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'ALL', 'AML', 'AML', 'AML', 'AML', 'AML', 'AML', 'AML', 'AML', 'AML', 'AML', 'AML']
  </code></pre>
  
  <p>This is trainData</p>
  
  <pre><code>[['-214' '-153' '-58' ..., '36' '191' '-37']
  ['-139' '-73' '-1' ..., '11' '76' '-14']
  ['-76' '-49' '-307' ..., '41' '228' '-41']
  ..., 
  ['-32' '-49' '49' ..., '-26' '133' '-32']
  ['-124' '-79' '-37' ..., '39' '298' '-3']
  ['-135' '-186' '-70' ..., '-12' '790' '-10']]
  </code></pre>
  
  <p>Below is the stack trace</p>
  
  <pre><code>Traceback (most recent call last):
  File "prediction.py", line 90, in &lt;module&gt;
    gaussianNaiveBayes()
  File "prediction.py", line 76, in gaussianNaiveBayes
    training = training.fit(trainData, target)
  File "/Library/Python/2.7/site-packages/sklearn/naive_bayes.py", line 163, in fit
    self.theta_[i, :] = np.mean(Xi, axis=0)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/ core/fromnumeric.py", line 2716, in mean
    out=out, keepdims=keepdims)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/core/_methods.py", line 62, in _mean
    ret = um.add.reduce(arr, axis=axis, dtype=dtype, out=out, keepdims=keepdims)
  TypeError: cannot perform reduce with flexible type
  </code></pre>