《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 npfrom 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

.dataframe thead tr:only-child th { text-align: right; } .dataframe thead th { text-align: left; } .dataframe tbody tr th { vertical-align: top; } 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()

key1a   -0.244128b    0.934956Name: data1, dtype: float64