Add column with previous values by group-CodePudding

I have got the following dataframe:

lst=[['01012021','A',10],['01012021','B',20],['02012021','A',12],['02012021','B',23]]
df2=pd.DataFrame(lst,columns=['Date','FN','AuM'])

I would like to add a column with the previous values by FN. As a result I should get the following dataframe:

df2=pd.DataFrame(lst,columns=['Date','FN','AuM','PreviousValues'])

Would you please help me?

CodePudding user response：

As the other answers pointed out, shift can be used to obtain adjacent values, but I think your intention is to use the previous values within a certain grouping. If that's the case, use groupby before shift.

df2['PreviousValues'] = df2.groupby('FN')['AuM'].shift()


       Date FN  AuM  PreviousValues
0  01012021  A   10             NaN
1  01012021  B   20             NaN
2  02012021  A   12            10.0
3  02012021  B   23            20.0

CodePudding user response：

use shift

df2['PreviousValues'] = df2['FN'].shift()

output:


        Date       FN   AuM PreviousValues
0       01012021    A   10  NaN
1       01012021    B   20  A
2       02012021    A   12  B
3       02012021    B   23  A

CodePudding user response：

Did you mean previous values of FN? If so, try to use

df2['PreviousValues'] = df2['FN'].shift(1)