How to calculate difference between two dates in different row and column?

[huhuhu]

Hello,

I'm wondering if there is a way to calculate the difference between two dates in different variables listed in different rows. My data looks like below:

MemberID   InDate     OutDate

1                  1/1/2019   1/3/2019

1                  1/4/2019   1/7/2019

2                  1/15/2019   1/16/2019

2                  1/20/2019    1/25/2019

Result that I'd like to have is

MemberID   InDate     OutDate            IntervalDays

1                  1/1/2019   1/3/2019           .

1                  1/4/2019   1/7/2019             1 (difference between 1/4/2019 and 1/3/2019)

2                  1/15/2019   1/16/2019          .

2                  1/20/2019    1/25/2019         4(difference between 1/20/2019 and 1/16/2019)

Any advice will be helpful!!

Thank you!

[Kurt_Bremser]

Use the lag() function to retrieve the value of a variable from the preceding observation.

[Jagadishkatam · Accepted solution]

Please try

data have;
input MemberID   InDate:mmddyy10.     OutDate:mmddyy10.;
format InDate OutDate date9.;
cards;
1 1/1/2019   1/3/2019
1 1/4/2019   1/7/2019
2 1/15/2019  1/16/2019
2 1/20/2019  1/25/2019
;

proc sort data=have;
by memberid indate outdate;
run;

data want;
set have;
by memberid indate outdate;
intervaldays=InDate-lag(OutDate);
if first.memberid then intervaldays=.;
run;

[huhuhu]

Thank you!