How to count distinct values with by condition

[LisaYIN9309]

Hi everyone. I have a data with multiple patients, each have one ore more rows, representing one or multiple pregnancies, even if a person has only one pregnancy, she can have more than one row (if she saw the doctor more than once during one pregnancy). I try to create a flag variable showing 'which pregnancy episode is this line of record indicates.'

To simplify the question, my input data looks like:

Note: although it looks in below simplified data that there are duplicate entries, but in my real data, the 'duplicate' row are different because I eliminate other variables/columns

data have;
input person_id condition_end_date;
datalines;
1 01/01/2014
1 01/10/2014
1 03/08/2015
1 03/08/2015
2 02/01/2014
2 09/08/2014
2 09/08/2014
2 06/07/2015
2 06/07/5015
;
run;

My output data, I want it to look like:

Person_id	Condition_end_date	Condition_id
1	01/01/2014	1
1	01/10/2014	2
1	03/08/2015	3
1	03/08/2015	3
2	02/01/2014	1
2	09/08/2014	2
2	09/08/2014	2
2	06/07/2015	3
2	06/07/2015	3

[LisaYIN9309]

I've tried something like below, but didn't work, I know the first. and last. part must have been wrong, but haven't figured out yet.

data test;
set have;
by person_id condition_end_date;
if first.condition_end_date then
   condition_id=1;
   else condition_id= condition_id+ 1;
if last.condition_end_date then
   output;
run;

Any suggestions is welcomed!

[RW9]

Something like:

data test;
  set have;
  by person_id condition_end_date;
  retain condition_id;
  if first.condition_end_date then condition_id=1;
  else condition_id=condition_id+1;
run;

[LisaYIN9309]

Thank you @RW9!

[PeterClemmensen · Accepted solution]

like this? Btw, I have corrected an error in your 'Have' data set as I'm guessing 5015 should be 2015 🙂

data have;
input person_id condition_end_date:mmddyy10.;
format condition_end_date mmddyy10.;
datalines;
1 01/01/2014
1 01/10/2014
1 03/08/2015
1 03/08/2015
2 02/01/2014
2 09/08/2014
2 09/08/2014
2 06/07/2015
2 06/07/2015
;
run;

proc sort data=have;
	by person_id condition_end_date;
run;

data want;
	set have;
	by person_id condition_end_date;

	if first.person_id then condition_id=1;
	else if first.condition_end_date then condition_id+1;

	retain condition_id;
run;

[LisaYIN9309]

Great, thank you so much @PeterClemmensen