indicator if drug taken on same or prior date

[Merdock]

Hi everybody,

I have dataset have below with participants who were given three meds: drug A, drug B and drug C.
I want to get dataset want below, where if the participant was given either drug on a previous date,
DRUGA (or DRUGB or DRUGC) then DRUGA (or DRUGB or DRUGC) turns from . to 2.

If no drug was used on that given date or a prior date then DRUGA (or DRUGB or DRUGC)=0. Otherwise, if drug was used on given date but not on any prior date, then DRUGA(or DRUGB or DRUGC)=1.

I have figured out a way to do, with code below but I want to know if there's a shorter, 
more efficient/elegant way of programming this.

Here are my have and want datasets, as well as the code I've come up with. 

Thanks in advance for any suggestions!

data have;
	length patid $25;
	input patid $ event $ date:mmddyy. diff  med DRUGA DRUGB DRUGC;
	format date mmddyy.;
	datalines;
P001 2 06/07/2017 1 1 . 1 .
P001 1 06/10/2017 . . . . .
P001 1 06/12/2017 . . . . .
P001 1 06/13/2017 . . . . .
P001 1 06/20/2017 . 1 . 1 .
P001 0 06/23/2017 . 1 . . 1
P001 0 06/24/2017 . 1 . . 1
P001 0 06/25/2017 . . . . .
P002 1 07/02/2019 . . . . .
P002 2 07/03/2019 1 1 . 1 .
P002 1 07/06/2019 . 1 1 . .
P002 1 07/10/2019 . . . . .
;
run;



data want;
	length patid $25;
	input patid $ event $ date:mmddyy. DRUGA DRUGB DRUGC;
	format date mmddyy.;
	datalines;
P001 1 06/10/2017 0 2 0
P001 1 06/12/2017 0 2 0
P001 1 06/13/2017 0 2 0
P001 1 06/20/2017 0 1 0
P001 0 06/23/2017 0 2 1
P001 0 06/24/2017 0 2 1
P001 0 06/25/2017 0 2 2
P002 1 07/02/2019 0 0 0
P002 1 07/06/2019 1 2 0
P002 1 07/10/2019 2 2 0
;
run;


data want;
	set have;
	by patid date;
	DRUGA_orig=DRUGA;
	DRUGB_orig=DRUGB;
	DRUGC_orig=DRUGC;

	retain DRUGA_imp DRUGB_imp DRUGC_imp;
	if first.patid then do;
		DRUGA=DRUGA_orig; DRUGA_imp=DRUGA_orig;
		DRUGB=DRUGB_orig; DRUGB_imp=DRUGB_orig;
		DRUGC=DRUGC_orig; DRUGC_imp=DRUGC_orig;
	end;
	array x1 DRUGA DRUGB DRUGC;
	array x2 DRUGA_imp DRUGB_imp DRUGC_imp;

	do i=1 to dim(x1);
		if x1[i]=.  then x1[i]=x2[i];	
		else             x2[i]=x1[i];
	end;
	drop i;

	*recode med indicator from 1 to 2 when drug taken on prior date;
	*recode med indicator from . to 0 when no drug taken prior to, or on the same date;
	array xdo1 DRUGA_orig DRUGB_orig DRUGC_orig;
	array xdo2 DRUGA DRUGB DRUGC;
	do j=1 to dim(xdo1);
		if xdo2[j]=.             then xdo2[j]=0;
		if xdo2[j]=1 & xdo1[j]=. then xdo2[j]=xdo2[j]+1;
	end;
	drop j;
	if diff=1 then delete; *delete EVID=2/diff=1 records;
run;

[PeterClemmensen]

A few questions : 

1) Can a patient receive more than 1 drug in 1 obs ? 

2) Do you want to delete all obs from have where diff = 1?

[Merdock]

1) Yes, a participant can receive more than 1 drug in 1 obs

2) Yes, the final dataset should only contain patid, evid, date and the drug indicators.

Thank you for your follow-up!