《利用python进行数据分析》学习笔记ch09

# 数据聚合与分组运算

GroupBy技术

import numpy as np
from pandas import DataFrame

df = DataFrame({'key1': ['a', 'a', 'b', 'b', 'a'],
'key2': ['one', 'two', 'one', 'two', 'one'],
'data1': np.random.randn(5),
'data2': np.random.randn(5)})
df

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	data1	data2	key1	key2
0	-0.361364	-0.417369	a	one
1	0.831824	0.841717	a	two
2	-0.569764	0.446787	b	one
3	0.723294	-1.248796	b	two
4	-0.813407	-0.384997	a	one

grouped = df['data1'].groupby(df['key1'])
grouped.mean()

key1
a   -0.244128
b    0.934956
Name: data1, dtype: float64