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Re: st: identifying variables


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: identifying variables
Date   Mon, 9 Apr 2012 08:57:58 +0100

You have provided yet another example of a problem in which -strpos()-
offers a simple alternative to -regexm()-.

That aside, your syntax is looking for the string "real" in the
_variable names_ themselves, for which

. findname *real*

would be a more obvious syntax, and indeed -describe *real*- would
work fine. Stata has a similar distinction in all string and regular
expression functions between looking in a string variable strvar and
looking in a variable name "varname".

. l in 1

     +-------------------------------------------+
     |     foo       bar     bazz    y         x |
     |-------------------------------------------|
  1. | reality   surreal   unreal   42   3.14159 |
     +-------------------------------------------+

. findname in 1, all(strpos(@, "real"))
foo   bar   bazz

. findname in 1, all(regexm(@, "[real]"))
foo   bar   bazz

. findname in 1, all(regexm(@, "real"))
foo   bar   bazz

@ is the default generic varname. -placeholder()- lets you specify an
alternative. You only need to specify "@" for searching the variable
names, but as above there are easier ways to do that.

Nick

On Mon, Apr 9, 2012 at 3:50 AM, Abhimanyu Arora
<abhimanyu.arora1987@gmail.com> wrote:

> I need to identify the variables for which the first observation
> contains the string "real".
> I used Nick Cox's -findname- from the SSC (updated 27 February 2012)
> in the following command.
>
> findname var1-var56 in 1,all(regexm("@","real+")) loc (varnames)
>
> But since -return list- comes up empty, something is amiss, perhaps in
> the use of the regular expression. May I also request some clarity in
> understanding of the role played by a "placeholder" in -findname-? As
> I see it, a generally character designated as a "placeholder" is
> supposed to take on supplied values—string or numerals. Or in other
> words, how would stata read the "@" in the above command?
>

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