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Re: st: Programming sub-routines

From   Nick Winter <[email protected]>
To   [email protected]
Subject   Re: st: Programming sub-routines
Date   Wed, 03 Nov 2004 16:12:49 -0500

You should read up on saving results in [U] 21.10.

The short version is that for returning value(s), usually you do an rclass program:

*------------beginning of mainprog.ado-------------------
program mainprog

... commands using r(whatever) , r(whichever) , etc....


program subprog, rclass

return scalar whatever = ...
return matrix whichever = ...
*------------end of mainprog.ado-------------------

For returning variables, you usually can send the name of the variable to be created or replaced as an argument to the subroutine:

*------------beginning of mainprog.ado-------------------
program mainprog

subprog `myvar'


program subprog
args variable


generate `variable' = ...


*------------end of mainprog.ado-------------------

Hope this helps
--Nick Winter

At 07:46 AM 11/4/2004 +1100, you wrote:

Dear Statalisters,

Before coming to Stata my programming was honed using Pascal and I'm
missing some of the tricks I used to access there. I would appreciate
any advice on a particular problem I have with Stata sub-routines.

I'm used to being able to modularise my programs (in Pascal) by having
lots of sub-routines for repetitive tasks, particularly functions
which carry out some kind of transformation. Some old database
languages (such as DBase) used to allow "user-defined" functions
for similar tasks.

I've tried to find the equivalent in Stata, but to no avail. If I use
a sub-routine inside a main program I can pass it arguments no
problem. But after doing some transformations on the arguments, how can I
send the results back to the main program? If I declare new local
macros to store the results, they disappear when I return to the main
program (because they're no longer in scope). If I declare global
macros, I can access the results back in the main program, but I'm
left with a lot of global macros. This appears to me bad practice, and
also requires lots of dropping of global macros on exit etc.

Am I missing something obvious? In Pascal terms arguments could be
"val" or "var" (the latter allowing for a return value). But in Stata all
arguments appear to only be "val". Is this right? Do I have any other
options? Any advice would be most appreciated.

Kind regards,

Ian Watson
Senior Researcher
University of Sydney
NSW 2006

Phone: 02 9351 5622
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