Title: Convert A Numeric Categorical Variable With Patsy
Slug: pandas_convert_numeric_categorical_to_numeric_with_patsy
Summary: Convert A Numeric Categorical Variable With Patsy
Date: 2016-05-01 12:00
Category: Python
Tags: Data Wrangling
Authors: Chris Albon



In [1]:

    
# import modules
import pandas as pd
import patsy



In [2]:

    
# Create dataframe
raw_data = {'countrycode': [1, 2, 3, 2, 1]} 
df = pd.DataFrame(raw_data, columns = ['countrycode'])
df









    Out[2]:






  
    
      
      countrycode
    
  
  
    
      0
      1
    
    
      1
      2
    
    
      2
      3
    
    
      3
      2
    
    
      4
      1



In [3]:

    
# Convert the countrycode variable into three binary variables
patsy.dmatrix('C(countrycode)-1', df, return_type='dataframe')









    Out[3]:






  
    
      
      C(countrycode)[1]
      C(countrycode)[2]
      C(countrycode)[3]
    
  
  
    
      0
      1.0
      0.0
      0.0
    
    
      1
      0.0
      1.0
      0.0
    
    
      2
      0.0
      0.0
      1.0
    
    
      3
      0.0
      1.0
      0.0
    
    
      4
      1.0
      0.0
      0.0