rare-encoding.py

def find_non_rare_labels(self, variable, tolerance):
        '''
        Function to check cardinality of a feature.
        Args: Dataframe, 
                Feature - Numerical Features,
                Tolerance - Threshold of number of values.
        Output: List of unique values of the feature.
        '''
        temp = self.data.groupby([variable])[variable].count() / len(self.data)
        non_rare = [x for x in temp.loc[temp>tolerance].index.values]
        return non_rare    
    
def rare_encoding(self, variable, tolerance):
        '''
        Encoding the rare labels to decrease cardinality
        Input: Dataframe, variable, 
                tolerance - Threshold value
        Ouput : dataframe with encoded values
        '''
        self.data = self.data.copy()
        # find the most frequent category
        frequent_cat = self.find_non_rare_labels(variable, tolerance)
        # re-group rare labels
        self.data[variable] = np.where(self.data[variable].isin(frequent_cat), self.data[variable], 'Rare')
        return self.data