Although I complain about the lack of a facility for user defined functions,
there is one area in which Stata's macro language surpasses SAS's. Due to
the way SAS implements macros, it is very cumbersome for a SAS program (the
rough equivalent of a Stata "do" file) to communicate with macros. In
Stata, you can write statements, such as "local num_obs = _N", to treat the
value of _N as text in subsequent macro program code. For example, I can
use the macro variable just created in lines, such as "gen var`num_obs' =
_n." You can't easily do this in SAS. In effect, Stata makes no
distinction at run-time between program code in an "ado" and code in a "do"
file that calls the "ado" program, whereas SAS translates all user written
procedures and functions into a standard SAS program prior to run-time.
Most important, Stata has built-in support for programmers interested in
extending it with procedures that resemble OEM commands. The error checking
for commands that follow standard syntax is a significant time saver for
those of us who want to maintain the look and feel of Stata when writing our
own procedures.
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Nick Cox
Sent: Tuesday, November 19, 2002 12:50 PM
To: [email protected]
Subject: st: RE: RE: RE: RE: RE: syntax question
David Moore
> There's at least one thing you can do with the SAS macro programming
> language that I have found useful. You can create
> functions. I know egen
> allows some limited capabilities with respect to new
> variable generation,
> but functions are more general. For example, they can be
> used to calculate
> or return values in many different programming contexts,
> not just to create
> variables.
True. That is, suppose you wanted to write
a Stata function to calculate logits. You could write
a -egen- function to create new variables, or
you could write -logitf- such that you could go
logitf 0.5
and it could print 0, and leave behind
r(logit)
so that you could go
logitf <argument>
... = r(logit)
So you can't define a function allowing you then to do
things like
. di logitf(0.5)
in just one line.
Nick
[email protected]
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