[英]Pandas - change the order of levels of factor-type object
I have a Pandas dataframe df
with column school
as factor 我有一个Pandas数据帧
df
,列school
作为因素
Name school
A An
B Bn
C Bn
How can I change the levels of the school
column from ('An', 'Bn') to ('Bn', 'An') in python? 如何在python中将
school
列的级别从('An','Bn')更改为('Bn','An')?
R equivalent is R等价物
levels(df$school) = c('Bn','An')
You can use reorder_categories
(you pass in the sorted factors): 您可以使用
reorder_categories
(传入已排序的因子):
In [11]: df
Out[11]:
Name school
0 A An
1 B Bn
2 C Bn
In [12]: df['school'] = df['school'].astype('category')
In [13]: df['school']
Out[13]:
0 An
1 Bn
2 Bn
Name: school, dtype: category
Categories (2, object): [An, Bn]
In [14]: df['school'].cat.reorder_categories(['Bn', 'An'])
Out[14]:
0 An
1 Bn
2 Bn
dtype: category
Categories (2, object): [Bn, An]
You can do this inplace: 您可以在现场执行此操作:
In [21]: df['school'].cat.reorder_categories(['Bn', 'An'], inplace=True)
In [22]: df['school']
Out[22]:
0 An
1 Bn
2 Bn
Name: school, dtype: category
Categories (2, object): [Bn, An]
See the reordering categories section of the docs . 请参阅文档的重新排序类别部分 。
You can set cat.categories
: 你可以设置
cat.categories
:
import pandas as pd
school = pd.Series(["An", "Bn", "Bn"])
school = school.astype("category")
school.cat.categories = ["Bn", "An"]
As a general solution, you can remap using a dictionary: 作为一般解决方案,您可以使用字典重新映射:
df = pd.DataFrame({'Name': ['A', 'B', 'C'],
'school': ['An', 'Bn', 'Bn']})
d = {'An': 'Bn', 'Bn': 'An'}
df['school'] = df.school.map(d)
>>> df
Name school
0 A Bn
1 B An
2 C An
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