How If-then-else works in SAS

[Hariharan1409]

While learning sas tutorial from PSU. @https://online.stat.psu.edu/stat480/lesson/welcome-stat-480.

I Came across these sentences:

Note that, in general, using ELSE statements with IF-THEN statements can save resources:

Using IF-THEN statements without the ELSE statement causes SAS to evaluate all IF-THEN statements. Using IF-THEN statements with the ELSE statement causes SAS to execute IF-THEN statements until it encounters the first true statement. Subsequent IF-THEN statements are not evaluated.

can someone explain me the above lesson with an example. Thanks.

[Kurt_Bremser · Accepted solution]

Suppose you have a variable x, which holds numerical values.

Both of these codes will yield the same result:

if x = 1 then y = 'A';
if x = 2 then y = 'B';
if x = 3 then y = 'C';

if x = 1 then y = 'A';
else if x = 2 then y = 'B';
else if x = 3 then y = 'C';

In the first code, all conditions will always be evaluated; in the second, if x equals 1, the second and third condition will not be evaluated, speeding up execution.

By evaluating for the most frequent value first, and the least frequent last, you can further optimize your code.

[Reeza]

This means that if you write your IF/THEN/ELSE statements in the order of what you expect to happen most frequently it will be faster than if you ordered them in some other order.