July 2019
Intermediate to advanced
365 pages
8h 13m
Chinese
Content preview from Python机器学习手册：从数据预处理到深度学习
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3.18
连接多个数据帧
｜
57
#
对行分组，然后在每一组上应用函数
dataframe.groupby('Sex').apply(lambda x: x.count())
Sex Name PClass Age Sex Survived SexCode
female 462 462 288 462 462 462
male 851 851 468 851 851 851
讨论
3.16
节提到过
apply
，当需要对所有分组应用一个函数的时候，
apply
非常有用。通过
联合使用
groupby
和
apply
，我们就能计算自定义的统计量，也能对每一组数据分别应
用任何函数。
3.18
连接多个数据帧
问题描述
连接（
concatenate
）两个数据帧。
解决方案
使用
concat
并设置参数
axis=0
，沿着行的方向来连接数据帧 ：
#
加载库
import pandas as pd
#
创建数据帧
data_a = {'id': ['1', '2', '3'],
'first': ['Alex', 'Amy', 'Allen'],
'last': ['Anderson', 'Ackerman', 'Ali']}
dataframe_a = pd.DataFrame(data_a, columns = ['id', 'first', 'last'])
#
创建数据帧
data_b = {'id': ['4', '5', '6'],
'first': ['Billy', 'Brian', 'Bran'], ...
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