Replace missing value with previous value

[Belle]

Thanks you all again. All the information are helpful. I learn so much from your all.

[Astounding]

SAS does contain a tool that may do exactly what you want.  Assuming your data are sorted:

data want;

  update have (obs=0) have;

  by id;

run;

That way, you can automatically expand this to many variables instead of just x, y, and z.

Good luck.

[anan]

Just another way

data want;

      set have;

      retain X_new Y_new Z_new ;

      by ID;

      array now(3) X Y Z;

      array three(3)X_new Y_new Z_new ;

      do i=1 to 3;

            if ID=lag(ID) then do;

                  if now(i)^=. then three(i)=now(i);

            end;

      end;

if last.ID then output want;

drop x y z;

run;