I have a dataframe imported from csv file below:

Houseid,Personid,Tripid,taz
1,1,1,4
1,1,2,7
2,1,1,96
2,1,2,4
2,1,3,2
2,2,1,58

There are three groups identified based on the combination of first and
second columns. How do I split this data frame?

I tried
aa <- split(inpfil, inpfil[,1:2])
but it has problems.

Output desired is

aa[1]
 Houseid,Personid,Tripid,taz
1,1,1,4
1,1,2,7
aa[2]
 Houseid,Personid,Tripid,taz
2,1,1,96
2,1,2,4
2,1,3,2
aa[3]
 Houseid,Personid,Tripid,taz
2,2,1,58

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