Question

I have a panel dataset and need to create an ID for groups of variables based on unique combination of (Year, LoadPort, DischargePort). There are other variables I would like to retain in the dataset but aren’t needed to identify the group. For example:

Year LoadPort  DischargePort ID
2007 ARZEW     LOOP TERMINAL 1
2008 ARZEW     LOOP TERMINAL 1
2011 RAS TANURA ZHONGSHAN    2
2010 RAS TANURA ZHONGSHAN    2

I need to create the last column. This is what I have tried but it gives me nonsense results:

proc sort data=data.benchmark5;
by loadport dischargeport year;
run;

data data.benchmark6;
   set data.benchmark5;
   retain ID;
   by loadport dischargeport year;
   if first.year then ID = 0;
   ID = ID + 1;
   run;

Answer 1

This would give you the ID as your sample shows.

data data.benchmark6;
 set data.benchmark5;
  if loadport^=lag(loadport) or DischargePort^=lag(DischargePort) then ID+1;
    else ID+0;
 run;