How to set calculation equation based on the value of a variable? Using loop or macro?

[CynthiaWei]

Hi SAS Pros,

I'm trying to create2 variables (as showed in the file - PT_pre and PT_post) to present the person-time patients have accrued in each stage, with the pre- and post-stage splits between T9 and T10.

Pre-stage:

The person-time for patients with outcome=1 in pre-stage should sum up the values from T1 until Tn, where Tn is determined by the value of outcome_timepoint (T5 for ID=XXXXX1).

The person-time for patients with outcome=0 in pre-stage should sum up the values from T1 until T9. 

Post-stage:

The person-time for patients with outcome=1 in post-stage should sum up the values from T10 until Tn, where Tn is determined by the value of outcome_timepoint (T13 for ID=XXXXX3). 

The person-time for patients with outcome=0 in post-stage should sum up the values from T10 until T20. 

For example, ID=XXXXX1 is outcome=1 at time point T5, so the person-time he contributed during pre-stage is PT_pre=sum(of T1-T5) (only T1=0, T2=1, T3=1, T4=0, and T5=1). Not every single time point this patient had contribution to person-time, so T1-T20 had both 0 or 1 value.  

I appreciate with any help!

Regards,

C

[SASJedi]

This DATA step builds your input data:

data have;
	infile datalines dsd dlm='|';
	input ID:$6. Outcome Outcome_timepoint:$3. T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T20;
datalines;
XXXXX1|1|T5|0|1|1|0|1|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|3|0
XXXXX2|0|NA|0|1|1|0|1|1|1|0|0|0|0|1|1|0|1|1|1|0|0|0|5|5
XXXXX3|1|T13|0|1|1|0|1|1|1|0|0|0|0|1|1|0|0|0|0|0|0|0|5|2
XXXXX4|0|NA|0|1|1|0|1|1|1|0|0|0|0|1|1|0|1|1|1|0|0|0|5|5
;

This DATA step performs the actions you specified:

data want;
	drop i;
	set have;
	array t[*] t:;
	if outcome=0 then do;
		PT_pre=sum(of t1-t9);
		PT_Post=sum(of t10-t20);
	end;
	else if outcome=1 then do;
		do i=1 to input(compress(outcome_timepoint,,'kd'),32.);
			PT_Pre=sum(PT_pre,t[i]);
		end;
		do i=10 to input(compress(outcome_timepoint,,'kd'),32.);
			PT_Post=sum(PT_pre,t[i]);
		end;
	end;
	else put "WARNING: Bad outcome value for " ID= outcome=;
run;

And this is the result:

Obs	ID	Outcome	Outcome_timepoint	T1	T2	T3	T4	T5	T6	T7	T8	T9	T10	T11	T12	T13	T14	T15	T16	T17	T18	T19	T20	PT_pre	PT_Post
1	XXXXX1	1	T5	0	1	1	0	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	3	.
2	XXXXX2	0	NA	0	1	1	0	1	1	1	0	0	0	0	1	1	0	1	1	1	0	0	0	5	5
3	XXXXX3	1	T13	0	1	1	0	1	1	1	0	0	0	0	1	1	0	0	0	0	0	0	0	7	8
4	XXXXX4	0	NA	0	1	1	0	1	1	1	0	0	0	0	1	1	0	1	1	1	0	0	0	5	5

Note that PT_POST for record 1 is missing, because you specified 
The person-time for patients with outcome=1 in post-stage should sum up the values from T10 until Tn, where Tn is determined by the value of outcome_timepoint 
The timepoint for observation 1 is T5, which is less than T10. What was your desired outcome for this row? Did you intend for this row to add up the values from T5 to T10?  

[CynthiaWei]

Hi,

Thank you so much for your help!

The desired outcomes are the person-time was accrued within its own period. Observation 1 developed outcome in T5, which is in pre-stage, then the expected PT_pre=sum(of T1-T9)=3. Observation 3 developed outcome in both pre- and post-stages, so the expected PT_pre=sum(of T1-T9)=5 and PT_post=sum(of T10-T20)=2. It looks like only the calculated results for observation 3 are not correct. Could you please advice how should I modify the code to cooperate my request? 

Again, I really appreciate it!

ID	Outcome	Outcome_timepoint	PT_pre	PT_Post	T1	T2	T3	T4	T5	T6	T7	T8	T9	T10	T11	T12	T13	T14	T15	T16	T17	T18	T19	T20
XXXXX1	1	T5	3	0	0	1	1	0	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
XXXXX2	0	NA	5	5	0	1	1	0	1	1	1	0	0	0	0	1	1	0	1	1	1	0	0	0
XXXXX3	1	T13	5	2	0	1	1	0	1	1	1	0	0	0	0	1	1	0	0	0	0	0	0	0
XXXXX4	0	NA	5	5	0	1	1	0	1	1	1	0	0	0	0	1	1	0	1	1	1	0	0	0