[R] Adding columns of Aggregates to existing dataframe

[tonyxv]

Hello,
I have a dataframe 


ID1   ID2
A1    B3
A1    B4
A1    B3
A1    B3
A2    B1
A2    B1
A2    B4
A3    B2
A3    B2
A5    B1
A5    B1
A5    B6
A5    B4
A6    B2



I want to add extra columns to the dataframe CountID1 and CountID2 which is
the actual count of values such as A1 etc
ie



ID1   ID2    CountID1    CountID2
A1    B3     4           3
A1    B4     4           4
A1    B3     4           3
A1    B3     4           3
A2    B1     3           4
A2    B1     3           4
A2    B4     3           3
A3    B2     2           3
A3    B2     2           3
A5    B1     4           4
A5    B1     4           4
A5    B6     4           1
A5    B4     4           4
A6    B2     1           3


I know this can be done by first creating temporary aggregate dataframes
then merging with the original.
Is there an easier way if i want to calculate many aggregates without having
to merge many temp tables.


Thanks.
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