title: Error unsupported operand type(s) for /: 'str' and 'int'
body: <p>I want to calculate the Mean of X columns as Matrix but got the subject error message however I have tried to convert the dataset to Integer through <code>Int</code> or <code>to_numeric</code> but didn't work</p>
  <pre><code>data = pd.read_csv('hw03_problem2.csv', skipinitialspace=True)
  trainingYdf = data['mpg']
  trainingXdf = data[['cylinders', 'displacement', 'horsepower', 'weight']]
  
  Y = np.matrix(trainingYdf).T
  X = np.matrix(trainingXdf)
  
  X_columnMeans = X.mean(axis=0)
  </code></pre>