looking for gaps in time spans for each memberID with multiple rows per memberID

[abqdiane]

Hello,

I have a list of members that can be enrolled in a club. Some members stay continuously enrolled, while other stop and start.  I'm trying to find those members who stopped  during the year and then re-enrolled and how long the gap is.  Each time a member re-enrolls, a new record is created. So some members will only have one record, but other could have 4 or 5 records.  In the example below, I have members for just one year, but the records go back for three to four years.  Any suggestions?  Would an array work?  I thought about transpose, but there are over 80,000 records.  I tried a retain function to come up with one row per member, but I couldn't get it to work.

From the  example below ,member 111 has 12 continuous months, but member 122 has a one month gap.  

I'd appreciate any help.

 ID Start_Date End_Date
111 01/01/2017 12/31/2017
122 01/01/2017 06/30/2017
122 08/01/2017 12/31/2017
133 01/01/2017 06/30/2017
133 07/01/2017 12/31/2017
144 1/1/2017 02/28/2017
144 04/01/2017 06/30/2017
144 08/01/2017 10/31/2017
144 11/01/2017 12/31/2017

[Astounding · Accepted solution]

Assuming your data set is sorted as indicated, you could use:

data want;

set have;

by id;

gap_size = start_date - lag(end_date);

if first.id = 0 and gap_size > 1;

run;

This gives you only the observations that begin after a gap.  If you want all the records, you could use a similar variation:

data want;

set have;

by id;

gap_size = start_time - lag(end_date);

if first.id then gap_size = 0;

run;

According to the examples you gave, there is no gap when gap_size is either 0 or 1.

[abqdiane]

Thanks so much -