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
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
>> 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?
>> more efficient way to generate new variables conditionally like this?
>> Paula D
>1) Your suggested syntax would mean that the meaning of the word "AND"
>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
>and then return 0 or 1 depending on the results of the comparisons.
>Your suggestion is that under certain conditions this expression should
>SAS to instead overwrite the contents of the two variables with the
>literals. The merit you ask for is consistency. I think making the
>of "AND" context-dependent like that would be undesirable. I'm curious -
>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
>If x22 = www then do;
> y32 = 'NA';
> Y100 = 'wa';