Richard Herrell
>
> 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.
I am still not clear whether -x- and -y- are variables,
and whether this all -- in Some Alternative
Software -- is tacitly looping over
observations. (In my case, please assume
complete ignorance of SAS.)
I will also add that I don't find often myself
wanting to use completely different
commands for different subsets of a variable.
Alternatives could depend on what those
commands are.
Nick
n.j.cox@durham.ac.uk
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/