机器学习实战1.4之逻辑回归：多分类问题解决方法

主要思想：将多分类问题转换为多个二分类问题。

import pandas as pd
import matplotlib.pyplot as plt

#由于数据集中每列数据没有标签，因此需要先手动添加，且用空格来隔开
columns = [
    'mpg', 'cylinders', 'displacement', 'horsepower', 'weight', 'acceleration',
    'model year', 'origin', 'car name'
]
cars = pd.read_table('./data/auto-mpg.data', delim_whitespace=True, names = columns)
print(cars.head())

    mpg  cylinders  displacement horsepower  weight  acceleration  model year  \
0  18.0          8         307.0      130.0  3504.0          12.0          70   
1  15.0          8         350.0      165.0  3693.0          11.5          70   
2  18.0          8         318.0      150.0  3436.0          11.0          70   
3  16.0          8         304.0      150.0  3433.0          12.0          70   
4  17.0          8         302.0      140.0  3449.0          10.5          70   

   origin                   car name  
0       1  chevrolet chevelle malibu  
1       1          buick skylark 320  
2       1         plymouth satellite  
3       1              amc rebel sst  
4       1                ford torino  

pandas.get_dummies()函数生成多分类标签

dummy_cylinders = pd.get_dummies(cars['cylinders'