pandas DataFrame对角线 [英] pandas DataFrame diagonal

问题描述

获得平方DataFrame的对角线的有效方法是什么.我希望结果是带有两个级别的Series和MultiIndex，第一个是DataFrame的索引，第二个级别是DataFrame的列.

What is an efficient way to get the diagonal of a square DataFrame. I would expect the result to be a Series with a MultiIndex with two levels, the first being the index of the DataFrame the second level being the columns of the DataFrame.

import pandas as pd
import numpy as np

np.random.seed([3, 1415])
df = pd.DataFrame(np.random.rand(3, 3) * 5,
                  columns = list('abc'),
                  index = list('ABC'),
                  dtype=np.int64
                 )

我想看看这个:

print df.stack().loc[[('A', 'a'), ('B', 'b'), ('C', 'c')]]

A  a    2
B  b    2
C  c    3

推荐答案

如果您不介意使用numpy，则可以使用numpy.diag

If you don't mind using numpy you could use numpy.diag

pd.Series(np.diag(df), index=[df.index, df.columns])

A  a    2
B  b    2
C  c    3
dtype: int64

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