I apologize. I was evidently not very clear judging by the confusion regarding this. Still, thank you for your help! To answer some of your questions in case someone else comes along and wants this valuable information, @ballardw wrote: From values in the data set how do we determine which value is the "value for Stimulation at time 0 from the alcohol session" and "Stimulation at time 0 from the placebo session" (not order in a picture but a rule, set of variable values or similar) These should be the variables highlighted in the red boxes. The output that I desire is Astimulation_tot (when order= alcohol) - Pstimulation_tot (when order= placebo) for each of the assessment_r that they share for each participant. @ballardw wrote: You do not have any variable labeled "time" so this is somewhat important. How do we identify "participant"? What role does drinking_session play? (I suspect that this has some correspondence to time 0 but you didn't tell us that). That was one of the comments I had as well is that "time" is really important here. I believe the "time" variable to be "assessment_r" as it ranges from 0 to 11 and repeats this pattern when order=placebo and order=alcohol. The participant is based on the "study_id" which is unique for each participant. Drinking_session is only ever 1 or 2. Some participants did alcohol first and some did placebo. Again, this is how I interpreted it as I got roughly the same description you got, but I do have the ability to ask him some questions. @ballardw wrote: Second is what does the desired output look like. This is some pseudo code that places a difference on what I think is the row with the placebo value. data want;
set have;
retain alc ;
by study_id drinking_session;
if first.study_id then alc=youralcoholvariable;
if first.drinking_session and drinking_session=2
then difference = alc -yourplacebovariable;
run; This assumes the data is sorted by study_id drinking_session and that the orders of the variables of interest appear on the first record the drinking session. It has been a long time since I did anything with SPSS and do not remember an equivalent to the SAS First and Last processing. Good luck. The desired output would be a new variable called "AmPStim" that would be the difference scores explained above. For instance, the first few would be 8-0 = 8; 54 - 3 = 51; 36-2= 34; 22-0= 22. The data is sorted by study_id. I appreciate you taking the time to write all this out for me! I can look up the first and last processing for SPSS as it has been a while for me as well.
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