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  2. Python | Pandas Series.diff ()

Python | Pandas Series.diff ()

Pandas Series.diff() is used to find differences between items in the same series. The difference is sequential and depends on the period parameter passed to the diff () method.

Syntax: Series.diff (periods = 1)

Parameters:
periods: integer value, subtracts element before / after period from current element. Negative values ​​are also accepted

Return type: Series

Example:
In this example two series are created from Python lists. The diff () method is called for both series, once with a positive period and once with a negative value passed to the period parameter.

# pandas module import

import pandas as pd 

 
# numpy module import

import numpy as np 

 
# create a list

list = [ 15 , 2 , 34 , 12 , 4 , 0 , 9 , 7 ]

 
# create series

series = pd.Series ( list )

 
# method call with period 2

period2 = series.diff ( 2 )

 
# Passing a negative value in the period
# passing period -1

period_1 = series.diff ( - 1 )

 
# display

print (`Diff with period 2 : {}

Diff with period - 1 : {} `. format (period2, period_1))

Exit:

 Diff with period 2: 0 NaN 1 NaN 2 19.0 3 10.0 4 -30.0 5 -12.0 6 5.0 7 7.0 dtype: float64 Diff with period -1: 0 13.0 1 -32.0 2 22.0 3 8.0 4 4.0 5 -9.0 6 2.0 7 NaN dtype: float64

Explanation: In the first output with a period of 2 digits The i-th position was subtracted from the (i + 2) th position and stored in the (i + 2) th position. In the second output, the value at the i-th position was subtracted from the values ​​in the (i-1) th position and stored in the (i-1) th position.

Note: Values ​​ First / Last n in the output series are equal to NaN depending on the sign of the period (first if the period is positive, and Last if it is negative, where n — period).