st: Efficient way to create adjacency matrix in Mata

[Benjamin Allaire <btallaire@hotmail.com>]

Listers -

Question: what is the most efficient way to create an adjacency matrix in mata, 
given a unique identifier ("id") and a club id ("club_id") for folks in the same club.

So the data looks like this:

id    club_id
1       1
2       1
3       2
4       2
5       2

Is there a clever way to do it without looping over the people? 

Any help would be most appreciated,

Thanks,
Ben

 		 	   		  
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