st: Merging two datasets multiple times

["Pavlos C. Symeou" <p.symeou@lmu.de>]

Dear Statalisters,

maybe you can assist with the following.

I have two datasets (A and B) which I need to merge.

Dataset A records a number of patents which are assigned multiple 
International Patent Classifications (ipc) as in:
id        ipc_1        ipc_2
1        AAAA        BBBB
2        AAAA        CCCC
3        DDDD     CCCC

Dataset B lists all IPCs in long format and for each IPC a set of 39 
characteristics as follows:
ipc          sic_1        sic_2        sic_3....          sic_39
AAAA      zzzzz          xxxxx           yyyyyy            eeeee
BBBB     tttttt            rrrrrr           ooooo           uuuuu
CCCC   www         gggg          pppp             qqqq


I want to merge datasets A and B so that the merged dataset looks like this:

id        ipc_1        ipc_2    sic_1        sic_2        sic_3....    
      sic_39     sic_40        sic_41        sic_42....          sic_78....
1        AAAA        BBBB     zzzzz          xxxxx           yyyyyy    
        eeeee      tttttt              rrrrrr             ooooo       
       uuuuu
2        AAAA        CCCC   zzzzz          xxxxx           yyyyyy        
    eeeee      www            gggg           pppp                 qqqq

Basically, for every patent I want to have all its IPCs and all SICs in 
the same row.

Best,

Pavlos

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