Using SPSS Reference Variables and an Index to Create a New Variable - indexing

Question

Essentially, I have a log which contains a Unique identifier for a subject which is tracked through multiple cases. I then used the following code, suggested previously through the great community here, to create an Index. Unfortunately, I've run into a new challenge that I can't seem to figure out. Here is a sample of the current data set to provide perspective.
Indexing function
sort cases by Unique_Modifier.
if $casenum=1 or Unique_Modifier<>lag(Unique_Modifier) Index=1.
if Unique_Modifier=lag(Unique_Modifier) Index=lag(Index)+1.
format Index(f2).
execute.
Unique Identifier Index Variable of interest
A 1 101
A 2 101
A 3 607
A 4 607
A 5 101
A 6 101
B 1 108
B 2 210
C 1 610
C 2 987
C 3 1100
C 4 610
What I'd like to do is create a new variable which contains the number of discrete, different entries in the variable of interest column. The expected output would be as the following:
Unique Identifier Index Variable of interest Intended Output
A 1 101 1
A 2 101 1
A 3 607 2
A 4 607 2
A 5 101 2
A 6 101 2
B 1 108 1
B 2 210 2
C 1 610 1
C 2 987 2
C 3 1100 3
C 4 610 3
I've tried a few different ways to do it, one was to use a similar index function, but it fails as if the variable of interest is different in subsequent lines, it works but, sometimes, we have a recurrence of a variable like 5 lines later. My next idea was to use the AGGREGATE function, but I looked through the IBM manual and it doesn't seem like there is a function within aggregate that would produce the intended output here. Anyone have any ideas? I think a loop is the best bet, but loops within SPSS are a bit funky and hard to get working.

Answer 1

Try this:
data list list/Unique_Identifier Index VOI (3f) .
begin data.
1 1 101
1 2 101
1 3 607
1 4 607
1 5 101
1 6 101
2 1 108
2 2 210
3 1 610
3 2 987
3 3 1100
3 4 610
end data.
string voiT (a1000).
compute voiT=concat(ltrim(string(VOI,f10)),",").
compute Intended_Output=1.
do if index>1.
do if index(lag(voiT), rtrim(voiT))>0.
compute Intended_Output=lag(Intended_Output).
compute voiT=lag(voiT).
else.
compute Intended_Output=lag(Intended_Output)+1.
compute voiT=concat(rtrim(lag(voiT)), rtrim(voiT)).
end if.
end if .
exe.