text: # Copyright 2020 Unibg Seclab (https://seclab.unibg.it)
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import scipy.stats
  
  
  # Functions to evaluate the cut-score of a column
  
  def entropy(ser):
      """Calculate the entropy of the passed `pd.Series`."""
      counts = ser.value_counts()
      return scipy.stats.entropy(counts)
  
  
  def neg_entropy(ser):
      """Revert the entropy sign to invert the column ordering."""
      return -entropy(ser)
  
  
  def span(ser):
      """Calculate the span of the passed `pd.Series`."""
      if ser.dtype.name in ('object', 'category'):
          return ser.nunique()
      else:
          return ser.max() - ser.min()
  