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Re: st: conditional "keep" statement


From   Eric Booth <ebooth@ppri.tamu.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: conditional "keep" statement
Date   Mon, 12 Apr 2010 09:16:47 -0500

>

You could use the extended macro function "subinstr" to filter the list in a loop (though I wonder if macro length limit will bite if you've got of hundreds or thousands of variable names):

*****
> local myvars  a1 a2 a3 d1 

ds
global mine `r(varlist)'
		di "$mine"
foreach v in  `myvars' {
	di "`v'"
	global mine: subinstr global mine "`v'" "",  word all
	}
		di "$mine"
drop "$mine"
*****
This should drop only those in the list that aren't in your `myvars' list.

~ Eric
__
Eric A. Booth
Public Policy Research Institute
Texas A&M University
ebooth@ppri.tamu.edu
Office: +979.845.6754




On Apr 12, 2010, at 8:54 AM, David Souther 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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