assign serial number

[Chung-Li]

Hi guys, 

I've encountered a problem that I couldn't understand why couldn't be solved.

Please take a look at the following dataset: (ID and Level are what I have, while Sn is what I want to generate)

ID    Level    Sn

1         L        1

1         L        1

            .

            .

            .
1         M        2

1         M        2

            .

            .

            .

2         H        3

2         H        3

            .

            .

            .

2         L        4

2         L        4

            .

            .

            .
2         M        5

2         M        5

            .

            .

            .

2         H        6

2         H        6

            .

            .

            .

General rule is that every subject has several records on three levels, and what I want to do is to generate serial number according to different levels for each subject.

I know it can be achieved by the combination of "do loop" and "by" statement.

However, the work just couldn't be done. (still trying)

Therefore, I post it to ask you guys for some help!

Thanks in advance!

Best regards, 

Bill

[andreas_lds · Accepted solution]

Try this:

data work.have;
   length id 8 level $ 1;
   input id level;
   datalines;
1 L
1 L
1 M
1 M
2 H
2 H
2 L
2 L
2 H
2 H
;
run;

data work.want;
   set work.have;
   length serial 8;
   retain serial 0;

   if level ^= lag(level) then do;
      serial = serial + 1;
   end;

run;

[Chung-Li]

Thanks, andreas!

I guess the problem is on "retain..."

However, I don't know why it should exist if there's already "serial=serial+1" 

But still thanks, you spot my blind point.