I have data arranged as follows:

id number 1 7 1 7 2 8 2 8 3 7 3 8 4 8 4 7 4 8 5 .

I would like to create a new variable (screen) that for each id, would indicate whether the 7 occurs for all records (1), only the 8 occurs (2), both occur (3) or none occur (4).

The final data would look like this:

id number screen 1 7 1 1 7 1 2 8 2 2 8 2 3 7 3 3 8 3 4 8 3 4 7 3 4 8 3 5 . 4

The tricky part is the third condition. I can't figure out how to determine when the values differ. My final dataset has over 500,000 records, so I'm hoping there is an efficient solution to this.

I would appreciate it if you could also cc your response to my private email; I don't always get all the mail from the list.

Thanks in advance for any help,

Frank Ivis