python - Pandas - 更改因子类型对象的级别顺序

Question

我有一个 Pandas 数据框 df，其中列 school 作为因子

Name    school
A       An
B       Bn
C       Bn

如何在 python 中将 school 列的级别从 ('An', 'Bn') 更改为 ('Bn', 'An')？

R 等价于

levels(df$school) = c('Bn','An')

Answer 1

您可以使用 reorder_categories (你传入排序的因素):

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]

您可以就地执行此操作:

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 .