Help with creating new variable with if-then statement (sas 9.4)

[Whitlea]

I am trying to create a variable that will indicate if both LDOS and FDOS are :

after span_end_2

and before after_cutoff_2

and before span_end_3. 

The issue I have is that in most cases, span_end_3 is blank/.  in which case the current code I have below will treat LDOS and FDOS as >  span_end_3.  I need to fix my code so sas will treat LDOS and FDOS as < span_end_3 when span_end_3 is blank. Is there a way to do this?

data have;
input
ID$	LDOS :DATE9.	FDOS :DATE9.	Span_Begin_1 :DATE9.	Span_End_1 :DATE9.	Span_Begin_2 :DATE9.
Span_End_2 :DATE9.	Span_Begin_3 :DATE9.	Span_End_3 :DATE9.	after_cutoff_2 :DATE9. ;

format FDOS MMDDYY10. LDOS MMDDYY10. Span_Begin_1 MMDDYY10. Span_End_1 MMDDYY10.  Span_Begin_2 MMDDYY10.
Span_End_2 MMDDYY10. Span_Begin_3  MMDDYY10. after_cutoff_2 MMDDYY10.;

datalines;

5	20Apr2023	20Apr2023	1Jul2022	    29Jul2022	21Nov2022	    4Apr2023	.	  .	    3Apr2024	
5	24Apr2023	24Apr2023	1Jul2022	    29Jul2022	21Nov2022    	4Apr2023	.	  .		3Apr2024	
5	25Apr2023	25Apr2023	1Jul2022	    29Jul2022	21Nov2022	    4Apr2023	.	  .		3Apr2024	
5	1May2023	1May2023	1Jul2022	    29Jul2022	21Nov2022    	4Apr2023	.	  .		3Apr2024	

;;;
run;

data want;
set have;

if LDOS gt Span_end_2 
and FDOS gt Span_end_2  
and LDOS lt after_cutoff_2
and FDOS lt after_cutoff_2 
and LDOS lt Span_end_3 
and FDOS lt Span_end_3 
then After_Span2=1;
else After_Span2=0;

run;

[mkeintz · Accepted solution]

Below is untested, but why not change

and LDOS lt Span_end_3 
and FDOS lt Span_end_3 

to

  and (span_end_3=. or LDOS lt Span_end_3 )
  and (span_end_3=. or FDOS lt Span_end_3 )

Editted note:

If you have instances of both span_end_3 and LDOS (or FDOS) the above suggestion would still pass the IF test.  If you want such situations to fail the test, then use

  and LDOS lt max(LDOS,Span_end_3)
  and FDOS lt max(FDOS,Span_end_3)

This will force both LDOS (or FDOS) and span_end_3 to be non-missing as well as satisfy the desired inequality.