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RE: st: Referencing individual elements of (local) macros


From   Nick Cox <n.j.cox@durham.ac.uk>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Referencing individual elements of (local) macros
Date   Fri, 3 Dec 2010 12:31:52 +0000

Also check out -tokenize- and a discussion in

SJ-3-2  pr0009  . . . . . . . . . . . . . Speaking Stata:  Problems with lists
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        Q2/03   SJ 3(2):185--202                                 (no commands)
        discusses ways of working through lists held in macros

Nick 
n.j.cox@durham.ac.uk 

Sergiy Radyakin

I salute your intent to use arrays for that: indeed you can do it with
arrays. Many statalisters
prefer variable lists instead. Given that you want only one var from
each list, just extract it
as a word by its index. See below.

If you are doing any data mining/optimal model search, investigate
further, e.g. see -bestreg-
by Zurab Sajaia:

net from http://adeptanalytics.org/download/ado/

sysuse auto

local depvars "price weight length"
local controlvars "rep78 foreign mpg"

local n_models : word count `depvars'
assert `n_models'==`:word count `controlvars''  // this ensures that
the two lists are of the same length

forval i=1/`n_models' {
	local this_depvar `: word `i' of `depvars''
	local this_controlvar `:word `i' of `controlvars''
	regress `this_depvar' `this_controlvar'
}


On Thu, Dec 2, 2010 at 4:03 PM, miros lav

> I am wondering whether it is possible to reference the individual
> elements of a (local) macro by a number. For example, if I have the
> local macro x "var1 var2 var3". How would something like reg y `x'[3]
> work.
>
> Long explanation:
>
> I would like to estimate a number of models with different dependent
> and independent variables. The control variable varies with the
> dependent variable. I would like to use some kind of loop structure
> (since I want to do a lot of estimations). so, I have defined two
> macros. Lets say that they each have three elements.
>
> local depvars " depvar1 depvar2 depvar3"
> local controlvars " controlvar1 controlvar2 controlvar3"
>
> I would like to do something like that
>
> i=1
> foreach c of local depvar{
> reg `c' `controlvars'[i]
> i++
> }
>
> Thanks for your help!

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