Calculate the time between the visits by group

[Sapt86]

Hi everyone, 

I'm quite new with SAS, and I wonder if you can please help me.

I'm trying to calculate time in days between the visits to the hospital of each client. That is, the idea is to know how many days pass between the client ends treatment and begins with a new treatment.

In my example, what I need, is the variable "Time between episodes (days)"

Client	Visits	Start Date	End Date	Time between episodes (days)
1	1	1/11/2019	3/11/2019	-
1	2	5/11/2019	11/11/2019	2
1	2	5/11/2019	11/11/2019	2
2	1	3/11/2019	3/11/2019	-
3	1	5/11/2019	7/11/2019	-
3	1	5/11/2019	7/11/2019	-
3	1	5/11/2019	7/11/2019	-
3	2	10/11/2019	15/11/2019	3
3	2	10/11/2019	15/11/2019	3

[Jagadishkatam · Accepted solution]

please try

data have;
input Client Visits	Start_Date:ddmmyy10. End_Date:ddmmyy10.;	
cards;
1 1 1/11/2019 3/11/2019  
1 2 5/11/2019 11/11/2019 
1 2 5/11/2019 11/11/2019 
2 1 3/11/2019 3/11/2019  
3 1 5/11/2019 7/11/2019  
3 1 5/11/2019 7/11/2019  
3 1 5/11/2019 7/11/2019  
3 2 10/11/2019 15/11/2019 
3 2 10/11/2019 15/11/2019 
;


data want;
set have;
by client visits Start_Date;
retain sdate edate;
if first.visits then edate= End_Date;
if first.visits then sdate=lag(edate)-Start_Date;
if first.client then sdate=.;
format Start_Date End_Date  edate date9.;
run;

[Sapt86]

Hi Jag, 

Thank you so much for your help! This worked perfectly fine for me. Thanks!