How to identify overlapping dates and assign them an identifier?

[reem225]

Hi,

I have a table with patient Id, treatment type, date of first prescription and date of last prescription. I want to create a new column (variable) which will return 1 if the first prescription date plus 30 days overlaps with the last prescription date, otherwise assign it a value of 0.  i tried using the retain function but no results. Can you please help me?

[PGStats]

Assuming your dates are SAS dates:

overlap = intnx("DAY", date, 30) >= lastdate;

[reem225]

Thank you so much!

they are sas dates and works!

[reem225]

I now noticed that once there is only 1 prescription and no last prescription the overlap is assigned as 1, is there a way to overcome that?

thank you

my code:

data overlap ;
		set Rxfinal ;
		by id date ;
	    lagtrt= lag(treatment);
	    if first.id then lagtrt=treatment;
		if not first.id then lagtrt=0 ; 
		switch = intnx("DAY", date, 30) >= lastdate;
		run ;