diff函数用法

基本用法

import pandas as pd
import numpy as np

df = pd.DataFrame(np.arange(12).reshape(3, 4), index=pd.date_range(start='20170101', periods=3),columns=['A','B','C','D'])

df

	A	B	C	D
2017-01-01	0	1	2	3
2017-01-02	4	5	6	7
2017-01-03	8	9	10	11

1、后一项减去前一项的差，记录在后一项位置

df1 = df.diff()

df1

	A	B	C	D
2017-01-01	NaN	NaN	NaN	NaN
2017-01-02	4.0	4.0	4.0	4.0
2017-01-03	4.0	4.0	4.0	4.0

df1.fillna(0)

	A	B	C	D
2017-01-01	0.0	0.0	0.0	0.0
2017-01-02	4.0	4.0	4.0	4.0
2017-01-03	4.0	4.0	4.0	4.0

2、右边减去左边的差值，记录在右边的位置

df2 = df.diff(axis=1)

df2

	A	B	C	D
2017-01-01	NaN	1.0	1.0	1.0
2017-01-02	NaN	1.0	1.0	1.0
2017-01-03	NaN	1.0	1.0	1.0

df2.fillna(0)

	A	B	C	D
2017-01-01	0.0	1.0	1.0	1.0
2017-01-02	0.0	1.0	1.0	1.0
2017-01-03	0.0	1.0	1.0	1.0