CODEWITHSUNDEEP
sas
hyg17
hyg17

Reputation: 237

How is the IF-THEN/ELSE condition working on this problem?

I am a bit puzzled why the output is a certain way on the following program.

 data a;
 input name$ lv @@;
 cards;
 Frank 1 Joan 2 Sui 3 Burt 4 Kelly . Juan 1
 ;
 data b;
 set a;
 if lv=.
 then expertise='?';
 else if lv=1 
       then expertise='L';
       else if lv=2 or 3 
            then expertise ='M';
            else expertise ='H';
 run;
 proc print data=b;
 run;

In the program above, I am expecting that the output for the observation containing Burt has expertise of value H, but for some reason it is M.

I was thinking that the if statement should be lv=(2 or 3) but when I do that now those that I am thinking that the lv= 2 and lv=3 whose expertise should equal M now becomes H as well.

*This is probably explained by the fact that the syntax is inappropriate, and lv is never (2 or 3) /I am not sure why this does not cause an error/ thus the ELSE statement is executed.

I have a feeling that I am not understanding how the ELSE is really working.

However, according to that logic then if the lv=2 part is recognized but the others are not, I am not sure why the lv= 3 and lv=4 does not produce an H.

My goal is to understand why the program runs as if there is no syntax error and why the output is what it is.

Upvotes: 1

Views: 72

Answers (2)

Tom
Tom

Reputation: 51611

Your syntax is incorrect, but not illegal, so SAS did what you asked for instead of what you wanted. The condition lv=2 or 3 is evaluated from left to right. So lv=2 will result in either 1 or 0 depending whether the value of lv is 2 or not. But both 1 or 3 and 0 or 3 will be true since 3 is always considered true.

What you really want is the in operator.

if missing(lv) then expertise='?';
else if lv=1 then expertise='L';
else if lv in (2 3) then expertise ='M';
else expertise ='H';

Upvotes: 2

Reeza
Reeza

Reputation: 21274

Your mistake is here 

If lv = 4 or 0

You think this means 

If lv = 4 or lv = 0

But it doesn’t. What actually happens is 

If (lv = 4) or 0

In SAS 0 is false and any number greater than 1 is true. Not sure about decimals. Anyways. The or condition makes this one false. But in your first example, it makes it always true.

Upvotes: 2

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