Pandas中pivot的使用

 pivot函数用于从给定的表中创建出新的派生表，pivot有三个参数：索引、列和值。具体如下：

def pivot_simple(index, columns, values):
    """
    Produce 'pivot' table based on 3 columns of this DataFrame.
    Uses unique values from index / columns and fills with values.
    Parameters
    ----------
    index : ndarray
        Labels to use to make new frame's index
    columns : ndarray
        Labels to use to make new frame's columns
    values : ndarray
        Values to use for populating new frame's values

pivot行转列函数: df.pivot() 将长数据集转换成宽数据集,

import pandas as pd
# 读取week数据集
week = pd.read_csv('data/week.csv')
week

	Name	Month	Week	Weight	Perc Weight Loss
6	Bob	Jan	Week 4	283	-0.027
7	Amy	Jan	Week 4	190	-0.036
14	Bob	Feb	Week 4	268	-0.053
15	Amy	Feb	Week 4	173	-0.089
22	Bob	Mar	Week 4	261	-0.026
23	Amy	Mar	Week 4	170	-0.017
30	Bob	Apr	Week 4	250	-0.042
31	Amy	Apr	Week 4	161	-0.053

# 用pivot重构DataFrame，让Amy和Bob的数据并排放置
winner = week.pivot(index='Month', columns='Name', values='Perc Weight Loss')
winner

Name	Amy	Bob
Month
Apr	-0.053	-0.042
Feb	-0.089	-0.053
Jan	-0.036	-0.027
Mar	-0.017	-0.026