如何将现有的单层列DataFrame转换为具有分层索引(MultiIndex)的列?
示例数据框:
In [1]:
import pandas as pd
from pandas import Series, DataFrame
df = DataFrame(np.arange(6).reshape((2,3)),
index=['A','B'],
columns=['one','two','three'])
df
Out [1]:
one two three
A 0 1 2
B 3 4 5
我认为reindex()应该有效,但是我得到了NaN:
In [2]:
df.reindex(columns=[['odd','even','odd'],df.columns])
Out [2]:
odd even odd
one two three
A NaN NaN NaN
B NaN NaN NaN
如果我使用DataFrame():
In [3]:
DataFrame(df,columns=[['odd','even','odd'],df.columns])
Out [3]:
odd even odd
one two three
A NaN NaN NaN
B NaN NaN NaN
这种方法实际上是有效的,如果我指定df.values:
In [4]:
DataFrame(df.values,index=df.index,columns=[['odd','even','odd'],df.columns])
Out [4]:
odd even odd
one two three
A 0 1 2
B 3 4 5
什么是正确的方法?为什么reindex()会产生NaN值?
df.columns = list(a)
。 - grabantot