Missing values and DO IF

* Working with missing values and DO IFs.

* The Syntax Reference Guide states:
*"Missing values returned by the logical expression on DO IF or on any ELSE IF cause control
* to pass to the END IF command at that point."

* rlevesque@videotron.ca.

DATA LIST FREE /a.
BEGIN DATA
1 . 1 .
END DATA.

COMPUTE b=a.

* Thus the following code.
DO IF a=1.
	COMPUTE a1=1.
ELSE IF MISSING(a).
	COMPUTE a1=2.
END IF.

* does NOT work because when the result of a=1 is missing, the execution immediately jumps to the END IF line. 
* The second condition MISSING(a) is never tested.

On the other hand the following works.

DO IF MISSING(b).
	COMPUTE b1=2.
ELSE IF b=1.
	COMPUTE b1=1.
END IF.