Find ids with at least two events that are less than 12 months apart

[lillymaginta]

I have a dataset with the ID and event date for each id. Each id can have many events up to 40 event dates. I want to find id who have at least 2 events that happened within no more than 12 months from each other. In the case below, the new dataset should keep id 1 and 3 because both have at least 2 even dates that are less than 12 months from each other 

id     event_Date
1      1/1/2005
1      2/21/2007
1      2/22/2007
1     12/5/2004
2     1/1/2004
2     3/3/2007
2     7/5/2006
3    11/2/2004
3     1/5/2005

[Ksharp]

But as your logic , 2 should be include too. 

2 3/3/2007
2 7/5/2006

only have 8 month between them .

[Kurt_Bremser]

Your rule and your wanted result don't match.

id 2 has less than 12 months between July 5, 2006 and March 3, 2007.

[Ksharp · Accepted solution]

OK. Assuming I follow your logic .

data have;
input id     event_Date : mmddyy10.;
format  event_Date  mmddyy10.;
cards;
1      1/1/2005
1      2/21/2007
1      2/22/2007
1     12/5/2004
2     1/1/2004
2     3/3/2006
2     7/5/2007
3    11/2/2004
3     1/5/2005
;
run;
proc sql;
create table want as
select * from have where id in (
 select distinct a.id 
  from have as a,have as b
   where a.id=b.id and a.event_Date ne b.event_Date and 
    abs(intck('month',a.event_Date,b.event_Date,'c')) le 12
);
quit;

[Kurt_Bremser]

If the aforementioned discrepancy was just a typo, this might be a solution:

data have;
input id event_date :mmddyy10.;
format event_date mmddyy10.;
cards;
1 1/1/2005
1 2/21/2007
1 2/22/2007
1 12/5/2004
2 1/1/2004
2 3/3/2007
2 7/5/2005
3 11/2/2004
3 1/5/2005
;
run;

proc sort data=have;
by id event_date;
run;

data want (keep=id);
set have;
by id;
retain flag;
prev_date = lag(event_date);
if first.id then flag = 0;
else do;
  if intck('month',prev_date,event_date,'cont') <= 12 then flag = 1;
end;
if last.id and flag then output;
run;

[lillymaginta]

Thank you both worked!

[Ksharp]

For the sake of safety and speed, I suggest you to use @Kurt_Bremser 's code , 

if there are two same event_date for the same ID , My code wouldn't be right.