Flag only once if the criteria is met

[novinosrin]

Ah I see @NickS2  I think still hung over from last night. My apologies. Try this

data want;
 do until(last.id);
  set have;
  by id ;
  trt_flag=' ';
  if visit=1 and ENROL_FLAG = "Y"  then do;
   trt_flag="Y";
   _n_=0;
  end;
  else if _n_ and ENROL_FLAG = "Y" and DAY_DIFF>180 then trt_flag="Y";
  if not _d and trt_flag="Y" then _d=date;
  if _d and date>=_d then output;
 end;
drop _d; 
run;

[NickS2]

@novinosrin 

This is exactly what I wanted. Thank you so much, you are a life saver.

[Jagadishkatam]

please try the below code

proc sort data=have;
by id drug date;
run;

data want;
set have;
by id drug date;
if first.drug and ENROL_FLAG='Y' then TRT_FLAG=ENROL_FLAG;
if not first.drug and ENROL_FLAG='Y' and  DAY_DIFF>180 then TRT_FLAG=ENROL_FLAG;
run;

[NickS2]

Thanks Jagdish,

But youe code is giving me the same result which I am getting.

[mklangley]

@NickS2 

Shouldn't the visit for patient 2 on 26JUN2016 (drug B) be flagged as TRT_FLAG = Y? Your desired output lists it as blank. The first criteria is not satisfied (since the patient already has had drug B), but the second is (ENROL_FLAG = Y and DAY_DIFF > 180).

[NickS2]

@mklangley No the second record for the patient ID 2 should be not get flagged because the first record already met the criteria.

[PGStats]

I think the proper logic would look like this:

proc sort data=have; by id drug date; run;

data want;
retain flagged;
set have; by id drug;
if first.drug then flagged = 0;
if not flagged then if ENROL_FLAG="Y" or DAY_DIFF > 180 then do;
    flagged = 1;
    TRT_FLAG = "Y";
    end;
drop flagged;
run;

proc sort data=want; by id date drug; run;