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RE: st: STATA Vs. SAS


From   Richard Herrell <rherre2@uic.edu>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: STATA Vs. SAS
Date   Wed, 27 Nov 2002 14:12:10 -0600 (CST)

On Wed, 27 Nov 2002, Nick Winter wrote:

> > -----Original Message-----
> > > In SAS, the code exits the structure when a true condition 
> > > is met.  In
> > > Stata, every if condition is evaluated even after the true 
> > > condition is
> > > met.
> > 
> > Perhaps we are not talking about 
> > the same thing here. I was assuming 
> > that -x- and -y- are _variables_. 
> > 
> 
> I took Richard's point to be that, *for each observation*, the
> evaluation of conditions only need take place until a true condition is
> found for *that observation*.  So, in the Stata code, Stata will
> evaluate three conditions per observation; SAS will evaluate fewer than
> that, depending on which conditions apply to which cases.


Yes, that's what I meant.  In my simple example, using the Stata
alternative isn't such a problem, but often I want to apply a subcondition
to only some values.  So, e.g.,

if x=0 then y=1;
else if 1 < x < 10 then do;
  <other sas commands>;
end;
else if 11 < x < 20 then do;
  <other sas commands>;
end;


It's difficult and tedious to have to write the multiple levels of
conditions if the program is going to evaluate every if statement.



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