How to fill in missing values?

[adventuresinsas]

I'm in bit of a pickle here and turning to you all for help. I'm a SAS beginner so pardon me if this is a very basic question. Basically, I have this dataset:

ID  Gender  Type

1    F            X

      F            Y

2    F            Y

      M           Y

      F            X

Both the first two observations "belong" to ID=1 and the last three observations "belong" to ID=2. How do I fill in the missing ID values? I've tried using retain but SAS won't let me run any data step where I have a "by id" statement because this dataset isn't sorted by id. However, I can't sort it by ID because then I lose the grouping.

Any solutions here?

[novinosrin · Accepted solution]

data want;

set have;

retain _id;

if not missing(id) then _id=id;

else id=_id;

drop _id;

run;