“仅对具有唯一值的索引对象有效的重新索引"； [英] "Reindexing only valid with uniquely valued Index objects"

问题描述

当我运行这样的代码时:

When I run code like this:

import pandas as pd

A = pd.DataFrame([('a', -1.374201, 35),
                  ('b', 1.415697, 29),
                  ('a', 0.233841, 18),
                  ('b', 1.550599, 30),
                  ('a', -0.178370, 63),
                  ('b', -1.235956, 42),
                  ('a', 0.088046, 2),
                  ('b', 0.074238, 84)], columns='key value other'.split())

B = A.groupby('key')['value'].mean()

C = pd.DataFrame([('a', 0.469924, 44),
                  ('b', 1.231064, 68),
                  ('a', -0.979462, 73),
                  ('b', 0.322454, 97)], columns='key value other'.split())

D = C.set_index('key')
D['value'] -= B

...最后一行失败并显示错误:

...the last line fails with the error:

Exception: Reindexing only valid with uniquely valued Index objects

我在做什么错了?

推荐答案

如果我正确地遵循了您的示例(感谢您添加示例，顺便说一句)，我相信您所需要的很简单:

If I follow your example correctly (thanks for adding it, BTW), I believe what you need is as simple as:

D.sub(B, axis='index')

哪个给我:

In [29]: D.sub(B, axis='index')
Out[29]: 
        value      other
key                     
a    0.777595  44.307671
a   -0.671791  73.307671
b    0.779919  67.548856
b   -0.128690  96.548856

如您所见，这弄乱了other列.如果这是一个问题，那么不幸的是，您又回到了相同的重复索引情况.

As you can see, this messes up the other column. If that's a problem, you're back in the same duplicate index situation, unfortunately.

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