Date:         Wed, 24 May 2000 08:39:41 -0400
Reply-To:     Howard Schreier <howard_schreier@ITA.DOC.GOV>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Howard Schreier <howard_schreier@ITA.DOC.GOV>
Subject:      Re: If Then Single ?

I believe that

    If x22 = www then y32 = 'NA' and Y100 = 'wa';

is interpreted as

    If x22 = www then y32 = ('NA' and (Y100 = 'wa'));

In other words, a comparison, then a boolean operation (involving implicit
type conversion), then an assignment.

There should be notes in the log about uninitialized variables and type
conversions.

On Wed, 24 May 2000 09:30:35 GMT, dkb@CIX.COMPULINK.CO.UK wrote:

>Paula D asks:
>
>> I know for fact that this does not work:
>>
>> If x22 = www then y32 = 'NA' and Y100 = 'wa';
>>
>> where x22 is a field read from original CSV data set and Y32 and y100 are
>> new variables. If 'if-then' is used to generate new variables, as I
wanted,
>> I have to do it one new variable a time. Otherwise, once x22 is evaluated
>> once, either 1 or 0 is assigned to x22 changing it from character to
>> numeric, screwing up the whole thing.
>>
>> Now my question is: why single only? what is the merit for doing that?
Any
>> more efficient way to generate new variables conditionally like this?
>>
>> Paula D
>
>Paula,
>
>1) Your suggested syntax would mean that the meaning of the word "AND"
should
>change depending on whereabouts in an expression it appears.
>Currently it's just a logical operator; when you code the expression
>y32 = 'NA' and Y100 = 'wa'
>you are directing SAS to compare the contents of two variables to two
literals
>and then return 0 or 1 depending on the results of the comparisons.
>Your suggestion is that under certain conditions this expression should
direct
>SAS to instead overwrite the contents of the two variables with the
specified
>literals.  The merit you ask for is consistency.  I think making the
behaviour
>of "AND" context-dependent like that would be undesirable.  I'm curious -
do
>you normally use another language that does behave like that?
>
>2) The syntax of if - then is simply
>if (condition) then (statement);
>The (statement) can be any valid SAS statement, in particular a DO, so you
can
>code
>If x22 = www then do;
>  y32 = 'NA';
>  Y100 = 'wa';
>end;
>
>
>Kind regards,
>
>Dave
>.