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st: create a variable based on a recurring value in a varlist

From   Derek Darves <>
Subject   st: create a variable based on a recurring value in a varlist
Date   Wed, 12 Oct 2005 20:04:31 -0700

Hi all,

I have a group of variables:

PID1 - PID15

PID* takes on values from 1 to 8000, and many are missing.

Basically, I would like to make a new variable, called interlock, that is equal to 1 if any of the variables in the list are equal to any other variable in the list (not including itself, of course).
For example, if PID5==705 and PID14==705 I would like like interlock==1

Likewise, if none of the the variables in PID* take on the value of any of the other variables in PID*, I would like interlock==0

I tried this:
egen interlock = group(pid1_a pid1_b pid2_a pid2_b pid3_a pid3_b pid4_a pid4_b pid5_a pid5_b pid6_a pid6_b pid7_a pid7_b pid8_a pid8_b pid9_a pid9_b pid10_a pid10_b pid11_a pid11_b pid12_a pid12_b pid13_a pid13_b pid14_a pid14_b pid15_a)

, but it returned all missing values when I know that some share a common value in two of the PID* fields.

Lastly, not that it should matter, but the above is a simplifying example. In my actual dataset I have about 130 PID* variables. I just mention this in case I am hitting some kind of memory limitation (I am not receiving any errors when I run the command, though, it just doesn't work).

Thanks in advance,


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