As the output from Example 5.1 illustrates, there may be occasions when you want to use an if-then-else statement instead of just an if-then statement. In that example, we told SAS only what to do if the condition following the IF keyword was true. By including an else statement, we can tell SAS what to do if the condition following the IF keyword is false.
Example 5.3 Section
The following SAS program creates a character variable status, whose value is "Failed" IF the student's first exam grade is less than 65, otherwise (i.e., ELSE) the value is "Passed":
DATA grades; input name $ 1-15 e1 e2 e3 e4 p1 f1; * if the first exam is less than 65 indicate failed; if (e1 < 65) then status = 'Failed'; * otherwise indicate passed; else status = 'Passed'; DATALINES; Alexander Smith 78 82 86 69 97 80 John Simon 88 72 86 . 100 85 Patricia Jones 98 92 92 99 99 93 Jack Benedict 54 63 71 49 82 69 Rene Porter 100 62 88 74 98 92 ; RUN; PROC PRINT data = grades; var name e1 status; RUN;
Launch and run the SAS program. Review the output from the PRINT procedure to convince yourself that the values of the character variable status have been assigned correctly.
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.
For greater efficiency, you should construct your IF-THEN-ELSE statements with conditions of decreasing probabilities.