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Re: st: conditional "keep" statement


From   Robert Picard <picard@netbox.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: conditional "keep" statement
Date   Mon, 12 Apr 2010 10:58:53 -0400

David,

You can build a new list that contains only existing variables by:

*--------------------------- begin example -----------------------

version 11

clear
sysuse auto

local myvars make bake price trunk turn shop

foreach v in `myvars' {
	capture confirm var `v'
	if !_rc local realvars `realvars' `v'
}

dis "`realvars'"

*--------------------- end example --------------------------

Robert

On Mon, Apr 12, 2010 at 9:54 AM, David Souther
<davidsoutheremail@gmail.com> wrote:
> I'm combining (append & merge) hundreds of files which contain
> hundreds or thousands of variables each, and at each stage of the
> merge/append, I'd like to variables only if they are in a list that I
> specify.
> The issue is that not all of these datasets contain all the variables
> in this list.  So, if I create a macro of my list,
>
> local myvars  a1 a2 a3 d1 d2 d3
>
> and then specify,
>
> keep `myvars'
>
> in the loop for each combination of data, I get the error that some
> variable doesn't exist when it's not in the dataset.  I tried getting
> around this with the -capture- command,
>
> cap keep `myvars'
>
> and using -ds-
>
> ds `myvars'
> keep `r(varlist)'
>
> or,
>
> ds `myvars', not
> drop `r(varlist)'
>
> and -ds- in combination with -capture- to no avail.   Any other ideas
> (besides specifying the hundreds of variables to keep for each/every
> loop)??
>
> D.S.
> *
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>

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