help with if

[NoorulIyn]

 data birth; input name $ bday :mmddyy10.; datalines; Miguel 12/31/1973 Joe 02/28/1976 Rutger 03/29/1976 Broguen 03/01/1976 Susan 12/12/1976 Michael 02/14/1971 LeCe 11/09/1967 Hans 07/02/1955 Lou 07/30/1960 ; 

data ages;
  set birth;
  retain current;
  if _n_=1 then current=today();
  format bday current worddate20.;
  age=int(intck('month',bday,current)/12);
  if month(bday)=month(current) then age=age-(day(bday)>day(current));
run;

proc print;
run;

How is the if condition solved here?Can someone explain it?Thanks.

[Reeza]

Which if condition?

The first states uses the automatic variable _n_, which essentially states if this is the first record in the dataset set the variable current to today.

[NoorulIyn]

Sorry for not being clear,the second if.(day(bday)>day(current)

[Reeza · Accepted solution]

That is comparison that returns true/false or 1/0. So if day(bday)>day(current) is true it becomes 1 and the equation becomes:

age=age-1;

otherwise it becomes:

age=age-0;

You can test it via

Y=day(bday)>day(current);

There's some details and comparisons on these formula's here:

https://communities.sas.com/thread/39473

I think intck with age option also calculates age correctly as of SAS 9.3+

[HarryLiu]

SAS evaluates the expression in an IF-THEN statement to produce a result that is either True or False (1 or 0). A result of zero causes the expression to be false, while a nonzero result causes the expression to be true.

Back to your question,

The MONTH function returns a numeric value that represents the month from a SAS date value. Numeric values can range from 1 (Jan.) through 12 (Dec.).

If month(bday)=month(current) means if the month of variable ‘bday’ is equal to current month.