问题描述
当我尝试将索引设置为某个值时，出现 ValueError: cannot reindex from a duplicate axis.我试图用一个简单的例子来重现这个，但我做不到.
I am getting a ValueError: cannot reindex from a duplicate axis when I am trying to set an index to a certain value. I tried to reproduce this with a simple example, but I could not do it.
这是我在 ipdb 跟踪中的会话.我有一个带有字符串索引、整数列和浮点值的 DataFrame.但是，当我尝试为所有列的总和创建 sum 索引时，我收到 ValueError: cannot reindex from a duplicate axis 错误.我创建了一个具有相同特征的小型 DataFrame，但无法重现问题，我会遗漏什么?
Here is my session inside of ipdb trace. I have a DataFrame with string index, and integer columns, float values. However when I try to create sum index for sum of all columns I am getting ValueError: cannot reindex from a duplicate axis error. I created a small DataFrame with the same characteristics, but was not able to reproduce the problem, what could I be missing?
我不太明白ValueError:无法从重复轴重新索引是什么意思，这个错误信息是什么意思?也许这会帮助我诊断问题，这是我问题中最容易回答的部分.
I don't really understand what ValueError: cannot reindex from a duplicate axismeans, what does this error message mean? Maybe this will help me diagnose the problem, and this is most answerable part of my question.
ipdb> type(affinity_matrix)
<class 'pandas.core.frame.DataFrame'>
ipdb> affinity_matrix.shape
(333, 10)
ipdb> affinity_matrix.columns
Int64Index([9315684, 9315597, 9316591, 9320520, 9321163, 9320615, 9321187, 9319487, 9319467, 9320484], dtype='int64')
ipdb> affinity_matrix.index
Index([u'001', u'002', u'003', u'004', u'005', u'008', u'009', u'010', u'011', u'014', u'015', u'016', u'018', u'020', u'021', u'022', u'024', u'025', u'026', u'027', u'028', u'029', u'030', u'032', u'033', u'034', u'035', u'036', u'039', u'040', u'041', u'042', u'043', u'044', u'045', u'047', u'047', u'048', u'050', u'053', u'054', u'055', u'056', u'057', u'058', u'059', u'060', u'061', u'062', u'063', u'065', u'067', u'068', u'069', u'070', u'071', u'072', u'073', u'074', u'075', u'076', u'077', u'078', u'080', u'082', u'083', u'084', u'085', u'086', u'089', u'090', u'091', u'092', u'093', u'094', u'095', u'096', u'097', u'098', u'100', u'101', u'103', u'104', u'105', u'106', u'107', u'108', u'109', u'110', u'111', u'112', u'113', u'114', u'115', u'116', u'117', u'118', u'119', u'121', u'122', ...], dtype='object')
ipdb> affinity_matrix.values.dtype
dtype('float64')
ipdb> 'sums' in affinity_matrix.index
False
这里是错误:
ipdb> affinity_matrix.loc['sums'] = affinity_matrix.sum(axis=0)
*** ValueError: cannot reindex from a duplicate axis
我试图用一个简单的例子来重现这个，但我失败了
I tried to reproduce this with a simple example, but I failed
In [32]: import pandas as pd
In [33]: import numpy as np
In [34]: a = np.arange(35).reshape(5,7)
In [35]: df = pd.DataFrame(a, ['x', 'y', 'u', 'z', 'w'], range(10, 17))
In [36]: df.values.dtype
Out[36]: dtype('int64')
In [37]: df.loc['sums'] = df.sum(axis=0)
In [38]: df
Out[38]:
10 11 12 13 14 15 16
x 0 1 2 3 4 5 6
y 7 8 9 10 11 12 13
u 14 15 16 17 18 19 20
z 21 22 23 24 25 26 27
w 28 29 30 31 32 33 34
sums 70 75 80 85 90 95 100
推荐答案
当索引具有重复值时加入/分配到列时，通常会出现此错误.由于您要分配给一行，我怀疑 affinity_matrix.columns 中存在重复值，可能未在您的问题中显示.
This error usually rises when you join / assign to a column when the index has duplicate values. Since you are assigning to a row, I suspect that there is a duplicate value in affinity_matrix.columns, perhaps not shown in your question.
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