Assign sequential id by two variables

[heretolearn]

Hello all,

I have a question about how to assign a sequential number by two variables.

Below is what I have:

Id         reg

1          1

1          1

1          3

1          3

1          3

1          4

2          2

2          2

2          2

2          3

Below is what I want:

Id         reg       reg_seq

1          1          1

1          1          1

1          3          2

1          3          2

1          3          2

1          4          3

2          2          1

2          2          1

2          2          1

2          3          2

Any advice?

[novinosrin]

data want;

set have;

by id reg;

if first.id then reg_seq=1;

else if first.reg the reg_seq+1;

run;

[PeterClemmensen]

data have;
input Id reg;
datalines;
1 1
1 1
1 3
1 3
1 3
1 4
2 2
2 2
2 2
2 3
;

data want;
   set have;
   by Id reg notsorted;
   if first.Id then reg_seq=1;
   else if first.reg the reg_seq+1;
run;