Keeping Only Observations Where Date Conditions are Met

[ssulli11]

Good afternoon!

I am trying to keep only data observations where an observation is "eligible" for all 12 months prior to their "firstDay".   As always, I so appreciate the help of the community! Thank you!

Have:

elg	inelg	firstDay	(Meets Criteria?)--Column not in dataset
DEC2009	DEC2014	2013-01-01	YES
FEB2007	MAR2010	2009-05-01	YES
OCT2016	OCT2017	2015-01-01	NO: Eligible after "FirstDay"
JAN1999	MAR2009	2009-09-01	NO: Eligibility ends before "FirstDay"
NOV2015	JAN2018	2016-01-01	NO" Not eligible for a full 12 months prior to "FirstDay"
SEP2013	DEC2017	2016-02-01	YES

Want:

elg	inelg	firstDay
DEC2009	DEC2014	2013-01-01
FEB2007	MAR2010	2009-05-01
SEP2013	DEC2017	2016-02-01

[PaigeMiller · Accepted solution]

Here's the logic ... compute 12 months before first day, then see if inelg is less than first day and 12 months before first day is after elg. This assumes your variables are actual SAS dates. (If they are not actual SAS dates, then you have to convert them to actual SAS dates and work on those)

data want;
    set have;
    twelve_months_before=intnx('month',firstday,-12,'b');
    if inelg>firstday and elg<=twelve_months_before then output;
run;

[ssulli11]

Thank you so much!  This was a much simpler solution that what I was trying to make work.