Dear all, 

I have a big problem: 
- I got two matrices, A and B 
- A shows identifies the value of B, however the values of B must be summed 
- For instance, 
1 1 2 2 
2 2 1 1 
gives matrix a 
3 4 2 1 
1 1 2 2 
gives matrix b 

Now the result for the value 1 would be 
7 
4 
which are the rowsums of the values of matrix B given that matrix A has the value 1. 


How can I do this automatically? I am really puzzled here. Thanks for your help guys, 
Tobi
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