st: how to make list of network ties from long data

[Caleb Southworth <caleb.southworth@gmail.com>]

I would like to make a list of people who are connected on some
identical variable, such as publishing in the same journal.

So I have . list date-magazine

     +----------------------------+
     | date   author     magazine |
     |----------------------------|
  1. | 1920    Woolf         Dial |
  2. | 1921    Woolf      Mercury |
  3. | 1930    Woolf       Nation |
  4. | 1925    Joyce         Dial |
  5. | 1930    Joyce   Transition |
     |----------------------------|
  6. | 1927        L         Dial |
  7. | 1930        L   Transition |
     +----------------------------+

And the desired outcome would be:

Woolf Joyce
Woolf L
Joyce Woolf
Joyce L
L Woolf
L Joyce

That is the pairs of who published in the same journal. I was working
to make a loop that establishes which authors share magazines in
common, but it seems like the long way around. Thanks.
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