python - OneHotEncoder 只有一个特征是字符串

Question

我希望将我仅有的一个特征转换为单独的二进制特征:

df["pattern_id"]
Out[202]: 
0       3
1       3
...
7440    2
7441    2
7442    3
Name: pattern_id, Length: 7443, dtype: int64 
df["pattern_id"]
Out[202]: 
0       0 0 1
1       0 0 1
...
7440    0 1 0
7441    0 1 0
7442    0 0 1
Name: pattern_id, Length: 7443, dtype: int64 

我想用OneHotEncoder，数据是int，所以不需要编码:

onehotencoder = OneHotEncoder(categorical_features=["pattern_id"])
df = onehotencoder.fit_transform(df).toarray()

ValueError: could not convert string to float: 'http://www.zaragoza.es/sedeelectronica/'

有趣的是我收到一个错误...sklearn 试图编码另一列，而不是我想要的。

我们必须将 pattern_id 编码为一个整数值

我使用了这个链接:Issue with OneHotEncoder for categorical features

#transform the pattern_id feature to int
encoding_feature = ["pattern_id"]
enc = LabelEncoder()
enc.fit(encoding_feature)
working_feature = enc.transform(encoding_feature)
working_feature = working_feature.reshape(-1, 1)
ohe = OneHotEncoder(sparse=False)


#convert the pattern_id feature to separate binary features
onehotencoder = OneHotEncoder(categorical_features=working_feature, sparse=False)
df = onehotencoder.fit_transform(df).toarray()

我得到了同样的错误。我做错了什么？

编辑

来源: https://github.com/martin-varbanov96/scraper/blob/master/logo_scrape/logo_scrape/analysis.py

df
Out[259]: 
      found_img  is_http                                           link_img  \
0          True        0                                  img/aahoteles.svg   
//www.zaragoza.es/cont/paginas/img/sede/logo_e...   

      pattern_id                                       current_link  site_id  \
0              3             https://www.aa-hoteles.com/es/reservas        3   
6              3      https://www.aa-hoteles.com/es/ofertas-hoteles        3   
7              2           http://about.pressreader.com/contact-us/        4   
8              3           http://about.pressreader.com/contact-us/        4   

      status                                   link_id  
0        200               https://www.aa-hoteles.com/  
1        200               https://www.365travel.asia/  
2        200               https://www.365travel.asia/  
3        200               https://www.365travel.asia/  
4        200               https://www.aa-hoteles.com/  
5        200               https://www.aa-hoteles.com/  
6        200               https://www.aa-hoteles.com/  
7        200              http://about.pressreader.com  
8        200              http://about.pressreader.com  
9        200               https://www.365travel.asia/  
10       200               https://www.365travel.asia/  
11       200               https://www.365travel.asia/  
12       200               https://www.365travel.asia/  
13       200               https://www.365travel.asia/  
14       200               https://www.365travel.asia/  
15       200               https://www.365travel.asia/  
16       200               https://www.365travel.asia/  
17       200               https://www.365travel.asia/  
18       200              http://about.pressreade 

[7443 rows x 8 columns]

Answer 1

如果您查看 OneHotEncoder 的文档您可以看到 categorical_features 参数需要“全部”或索引数组或掩码不是字符串。您可以通过更改为以下行来使您的代码工作

import pandas as pd
from sklearn.preprocessing import OneHotEncoder
# Create a dataframe of random ints
df = pd.DataFrame(np.random.randint(0, 4, size=(100, 4)),
                  columns=['pattern_id', 'B', 'C', 'D'])
onehotencoder = OneHotEncoder(categorical_features=[df.columns.tolist().index('pattern_id')])
df = onehotencoder.fit_transform(df)

但是 df 将不再是 DataFrame，我建议直接使用 numpy 数组。