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Re: st: Re: problem with -capture drop-

From   [email protected] (Jeff Pitblado, Stata Corp.)
To   [email protected]
Subject   Re: st: Re: problem with -capture drop-
Date   Tue, 21 Oct 2003 16:36:12 -0500

Eddy <[email protected]> asks about dropping variables:

> Thanks for the explanation, but I still cannot fathom the logic of
> this implementation. If I want to drop a single or all variables
> begining with r, I shall use a wildcard like r*, no matter whether I
> have only one variable beginning with r in the dataset or not. If I
> want to drop the literatral "r", I shall be able to do so by
> specifying -capture drop r-.
> Anyway, the practical issue here is: Is there a way to stop Stata
> from playing smart in this type of situation? Thanks.

Eddy can check that the variable "r" truly exists by using the -unab- command.
For example, in Stata 8, Eddy could try:

	. capture unab uv : r
	. if (!c(rc) & "`uv'" == "r") drop r

Here is a short program that will loop over its arguments (variable names),
and will drop a variable if it explicitly matches a specified name.

***** BEGIN: drop2.ado
program drop2
	version 8.1
	while `"`0'"' != "" {
		gettoken v 0 : 0
		capture unab uv : `v'
		if (!c(rc) & "`uv'" == "`v'") drop `v'
***** END: drop2.ado

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