Date:         Thu, 13 Apr 2006 16:53:33 -0400
Reply-To:     Chang Chung <chang_y_chung@HOTMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Chang Chung <chang_y_chung@HOTMAIL.COM>
Subject:      Re: Code for higher order neighbor generation
Comments: To: I X <imamx8@GMAIL.COM>

On Thu, 13 Apr 2006 15:55:59 -0400, Imam Xierali <imamx8@GMAIL.COM> wrote:

>Some of you ask about my code for second order neighbor generation in SAS. I
>am here pasting it to the email itself, the code works, though it can be
>improved. The direct connectivity dataset is from www.correlatesofwar.org.
...

Hi, Imam,

Thanks for sharing your code. I am a bit puzzled by its length and
complexity. Maybe you are doing way more than you say what you are doing.
Because finding out the "second order neighbors," given a list of the "first
order neighbors" can be as simple as below. Or am I missing something?

Cheers,
Chang

data neighbors;
  input from to;
cards;
1 2
1 3
2 4
2 5
3 7
4 8
;
run;

proc sql;
  title "second order neighbors";
  select a.from, a.to as through, b.to
  from   neighbors as a, neighbors as b
  where  a.to = b.from
  order by a.from, b.to
  ;
quit;
title;
/* on lst
second order neighbors

    from   through        to
----------------------------
       1         2         4
       1         2         5
       1         3         7
       2         4         8
*/