/* this program creaets a simple peer influence effect as 
  an example.

*/

libname in1xpt xport 'c:\jwm\conferences\columbia\workshop\sdatcln.xpt';
libname in1 'c:\jwm\conferences\columbia\workshop\';

/* bring in the base school data */
data sdat;
 set in1xpt.sdatcln;
 run;

/* load the network and create the measures */

 proc iml;
  reset storage = in1.netstore;
  load amatis amatis_id;

  use work.sdat;
   read all var{s48} into tryhard;
   read all var{s64} into fights;


   /* to get a peer influence vector, you want to weight the value of 
      each person by the adjacency.  This is a simple matrix multiplication
   */

   /* because IML doesn't play well w. missing values, we want
      to do some counts first to correct for that */

   thdat=choose(tryhard=.,0,1); /* flags non-missing tryhard data */
   fgdat=choose(fights=.,0,1); /* flags non-missing fight data */


   tryhard=choose(tryhard=.,0,tryhard); /* means that ego's non-responding
   											alter's don't count */
   fights=choose(fights=.,0,fights);


   /* lots of ways to get the peer influence measure.  Here I use matrix mult and 
      then divide by number w. non-missing data.  We could also simply create 
      a weight by out-degree and then row-normalize the adj. matrix */

   symnet=(amatis+amatis`); /* will equal 1 if i-->j or j-->i, 2 if i<-->j */
   peertry=symnet*tryhard; /* sum of edge value times data value */
   ptrydat=(symnet>0)*thdat; /* count of ego's alters w. non-missing data */
   th_pmean=peertry/ptrydat;

   peerfgt=symnet*fights;
   pfgtdat=(symnet>0)*fgdat;
   fgt_pmean=peerfgt/pfgtdat;

   totdeg=(symnet>0)[,+];

   outd=amatis_id||th_pmean||fgt_pmean||totdeg;
   create work.peermeans from outd [colname={nid tryhard_pm fights_pm totdeg}];
   append from outd;
   quit;

data sdat;
 merge sdat peermeans;
 by nid;
 run;

proc reg data=sdat;
 model s48 = female white s3 tryhard_pm;
 run; quit;

proc reg data=sdat;
 model s64 = female white s3 fights_pm;
 run; quit;

 proc genmod data=sdat;
      model s64 = female white s3 fights_pm / dist   = nor
                          link   = id;
   run;

 proc genmod data=sdat;
      model s48 = female white s3 tryhard_pm / dist   = nor
                          link   = id;
   run;


/* we know the assumptions of the model are violated, so let's try
   a QAP model on the dyad, which is more conservative */