[英]pandas reset_index after groupby.value_counts()
I am trying to groupby a column and compute value counts on another column.我正在尝试对一列进行分组并计算另一列上的值计数。
import pandas as pd
dftest = pd.DataFrame({'A':[1,1,1,1,1,1,1,1,1,2,2,2,2,2],
'Amt':[20,20,20,30,30,30,30,40, 40,10, 10, 40,40,40]})
print(dftest)
dftest looks like dftest 看起来像
A Amt
0 1 20
1 1 20
2 1 20
3 1 30
4 1 30
5 1 30
6 1 30
7 1 40
8 1 40
9 2 10
10 2 10
11 2 40
12 2 40
13 2 40
perform grouping进行分组
grouper = dftest.groupby('A')
df_grouped = grouper['Amt'].value_counts()
which gives这给
A Amt
1 30 4
20 3
40 2
2 40 3
10 2
Name: Amt, dtype: int64
what I want is to keep top two rows of each group我想要的是保留每组的前两行
Also, I was perplexed by an error when I tried to reset_index
另外,当我尝试
reset_index
时,我对错误感到困惑
df_grouped.reset_index()
which gives following error这给出了以下错误
df_grouped.reset_index() ValueError: cannot insert Amt, already exists
df_grouped.reset_index() ValueError: 无法插入 Amt,已经存在
You need parameter name
in reset_index
, because Series
name is same as name of one of levels of MultiIndex
:您需要
reset_index
参数name
,因为Series
名称与MultiIndex
级别之一的名称相同:
df_grouped.reset_index(name='count')
Another solution is rename
Series
name:另一种解决方案是
rename
Series
名称:
print (df_grouped.rename('count').reset_index())
A Amt count
0 1 30 4
1 1 20 3
2 1 40 2
3 2 40 3
4 2 10 2
More common solution instead value_counts
is aggregate size
:更常见的解决方案是
value_counts
是聚合size
:
df_grouped1 = dftest.groupby(['A','Amt']).size().reset_index(name='count')
print (df_grouped1)
A Amt count
0 1 20 3
1 1 30 4
2 1 40 2
3 2 10 2
4 2 40 3
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.