show date as a blank based on condition

[Q1983]

data have;
date1='01jan2021'd;
date2='01jan2021'd;
date3='31mar2021'd;
format date1 date2 date3 date9.;
yr_date1 = put(date1,monyy7.);
yr_date2 = put(date2,monyy7.);
yr_date3 = put(date3,monyy7.);
if yr_date1 <>yr_date2 then date2 = .;
if yr_date1 <>yr_date3 then date3 = .;
run;

I have 3 dates.  Using date1 as the base, If the month and year are a match in date1 and date2 I want to show date2.  Same for the relationship between date1 and date3.  The only way I knew to handle was to convert the dates to string (ie date1 put statement).  if yr_date1 <>yr_date2 then date2 = .; if yr_date1 <>yr_date3 then date3 = .;  In this case date1 and date3 are not a match so I want date3 to show a blank.  However a value still shows for date3. 

[jimbarbour · Accepted solution]

How about something like this:

data have;
	date1='01jan2021'd;
	date2='01jan2021'd;
	date3='31mar2021'd;
	format date1 date2 date3 date9.;
run;

data	want;
	DROP	_:;
	set have;
	_Year_Mon1	=	(YEAR(date1) * 100) + MONTH(date1);
	_Year_Mon2	=	(YEAR(date2) * 100) + MONTH(date2);
	_Year_Mon3	=	(YEAR(date3) * 100) + MONTH(date3);

	IF	_Year_Mon2	^=	_Year_Mon1	THEN
		CALL	MISSING(Date2);

	IF	_Year_Mon3	^=	_Year_Mon1	THEN
		CALL	MISSING(Date3);
run;

If you want to do this with a larger dataset, there would probably need to be some adjustments, but the YEAR() and MONTH() functions should still do what you would need.  If there were more dates per record than 3, it might be worth converting the code to use an array.

Jim