Hi,
   
  How can I accomplish this in R. Example:
   
  R1  R2
  3     101
  4     102
  3     102
  18    102
  11    101
   
  I want to find Sum(101) =  14 - i.e SUM(R1) where R2 = 101
                  Sum(102) = 25    - SUM(R2) where R2 = 102
   
  TIA
  Sachin

		
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