Row by row duplicate compare and flag in both

[Madhav4114]

Input
Id. Date
1. 200701
1 200701
1 200702
2 201001
2 201002
2. 201002
Need output where in flag has 1 for both duplicate rows

Output
Id Date flag
1. 200701. 1
1 200701. 1
1 200702. 0
2 201001. 0
2 201002. 1
2. 201002. 1

[Kurt_Bremser]

data want;
set have;
by id date;
flag = (first.date ne last.date);
run;

[Madhav4114]

In this , if I add one more duplicate row then it will flag 0 in between

[Astounding]

Here's a variation to take care of that:

data want;
   set have;
   by id date;
   retain flag 0;
   if first.date then 
      flag = (last.date=0);
run;

[Kurt_Bremser · Accepted solution]

---

@Madhav4114 wrote:
In this , if I add one more duplicate row then it will flag 0 in between

---

Then do this:

data want;
set have;
by id date;
flag = (not first.date or not last.date);
run;