Create a new variable in SPSS based on different cases with the same "id" variable

Question

I have a dataset which, in some cases, contains data of a particular score from multiple time points "score1" and "score2". So I want to create a new variable "prospective"=1 which identifies the cases with prospective data (same "id" and with "score1" and "score2" data available). Thus, it should look something like this:

Therefore, if the "id" is the same but the score is missing in one of the different time points, it should return "prospective"=0. I have tried using the LAG function, something like this:

DO IF (id = LAG(id)) AND ((Score1 GE 0) OR (Score2 GE 0)) AND ((LAG(Score1) GE 0) OR (LAG(Score2) GE 0)).
Compute LAG(Prospective = 1) AND Prospective =1.
END IF.
Execute.

However, I get an error saying that an equal sign was not found when expected after a target variable in a COMPUTE command.

I would really appreciate it if you could help me. Thank you!

Answer 1

The following code will count the valid values in each row for every ID, then aggregate the count across both rows of the ID. Then ID's with a count of two valid values will be marked as prospective=1 (the others - 0):

compute validsRow=2-nmiss(score1,score2).
aggregate out=* mode=addvariables overwrite=yes /break=id /validsID=sum(validsRow).
compute prospective=validsID=2.
exe.