Add End Date to previous record

[Mounika2]

output-

pt     element          Start_date      end_date

101 screening        2017-02-10   2017-02-24
101 randomization 2017-02-24   2017-03-05
101 treatment        2017-03-05   2017-09 -23
101 followup          2017-09-23   2017-02-12

102 screening        2017-02-12   2017-02-22
102 randomization 2017-02-22   2017-03-10
102 treatment        2017-03-10   2017-09-20
102 followup          2017-09-20   2017-09-20

 data raw (rename= (visit= ELEMENT));
input pt visit$9. STDT: is8601da.;
format STDT is8601da.;
datalines;
101 screening        2017-02-10
101 randomization 2017-02-24
101 treatment        2017-03-05
101 followup          2017-09-23 

102 screening        2017-02-12   
102 randomization 2017-02-22   
102 treatment        2017-03-10   
102 followup          2017-09-20   
run;

[PeterClemmensen]

Are you sure this is the output you want? As I see it, you fetch the Start_Date of the screening for pt 102 as the end_date for the followup for pt 101? I don't think this is desirable?

[PeterClemmensen · Accepted solution]

I think this is what you want

data raw (rename= (visit= ELEMENT));
input pt visit :$13. STDT: is8601da.;
format STDT is8601da.;
datalines;
101 screening 2017-02-10
101 randomization 2017-02-24
101 treatment 2017-03-05
101 followup 2017-09-23 
102 screening 2017-02-12 
102 randomization 2017-02-22 
102 treatment 2017-03-10 
102 followup 2017-09-20 
run;

data want;
   merge raw(rename=STDT=start_date) raw(firstobs=2 rename=STDT=end_date keep=STDT);
   if ELEMENT='followup' then end_date=start_date;
run;