Flag presence/absence based in a variable values

[NewUsrStat]

Hi guys, 

suppose to have the following: 

data have;
  input ID $ (Start End) (:date.) Place $;
  format start end date9.;
cards;
0001 13JAN2015 20JAN2015 0
0001 21JAN2015 31DEC2015 1
0001 01JAN2018 31DEC2018 0
0001 01JAN2019 31DEC2019 1
0002 01JAN2015 31DEC2015 1
0002 01JAN2019 31OCT2019 0
0002 01NOV2019 31DEC2020 0
;

Is there a way to add two variables (with 1 = yes, 0= no): one indicating the first date the patient has Place = 1 ever in his life and another indicating the first date the patient has Place = 0 ever in his life? 

Desired output: 

data have;
  input ID $ (Start End) (:date.) Place First_1 First_0 $;
  format start end date9.;
cards;
0001 13JAN2015 20JAN2015 0 0  1
0001 21JAN2015 31DEC2015 1 1  0
0001 01JAN2018 31DEC2018 0 0  0
0001 01JAN2019 31DEC2019 1 0  0
0002 01JAN2015 31DEC2015 1 1  0
0002 01JAN2019 31OCT2019 0 0  1
0002 01NOV2019 31DEC2020 0 0  0
;

Thank you in advance

[ballardw · Accepted solution]

data have;
  input ID $ (Start End) (:date.) Place $;
  format start end date9.;
cards;
0001 13JAN2015 20JAN2015 0
0001 21JAN2015 31DEC2015 1
0001 01JAN2018 31DEC2018 0
0001 01JAN2019 31DEC2019 1
0002 01JAN2015 31DEC2015 1
0002 01JAN2019 31OCT2019 0
0002 01NOV2019 31DEC2020 0
;

proc sort data= have;
   by id place start;
run;

data want;
   set have;
   by id place start;
   first_1 = (first.place and place='1');
   first_0 = (first.place and place='0');
run;

proc sort data=want;
   by id start;
run;

First and/or Last are available with BY group processing in a data step. Each variable on the BY has its own indicator accessed using the First.Variable or Last.Variable. The values are 1 for True or 0 for False.

And why is your "place" variable character if it only has 1 and 0 for values? Kind of odd.

[Ksharp]

data have;
  input ID $ (Start End) (:date.) Place ;
  format start end date9.;
cards;
0001 13JAN2015 20JAN2015 0
0001 21JAN2015 31DEC2015 1
0001 01JAN2018 31DEC2018 0
0001 01JAN2019 31DEC2019 1
0002 01JAN2015 31DEC2015 1
0002 01JAN2019 31OCT2019 0
0002 01NOV2019 31DEC2020 0
;

data want;
 set have;
 by id;
 retain found_1 found_0 ;
 if first.id then call missing(found_1,found_0);
 first_1=0;first_0=0;
 if Place=1 and not found_1 then do;first_1=1;found_1=1;end;
 if Place=0 and not found_0 then do;first_0=1;found_0=1;end;
 drop found_:;
run;