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Re: st: Generating dummies with xi


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Generating dummies with xi
Date   Tue, 12 Apr 2011 08:36:43 +0100

Good point. My statement was an oversimplification. It very much needs
a qualification: when there is a choice.

Nick

On Tue, Apr 12, 2011 at 2:37 AM, Garry Anderson
<g.anderson@unimelb.edu.au> wrote:

> I think another exception to use -xi:- with Stata 11, rather than use
> factor variables, is when the following estimation commands are being
> used
> -exlogistic-, -expoisson-, -qreg-, -iqreg-, -sqreg- and -bsqreg-.
>
> There may be other commands that do not allow factor variables.
>
> Best wishes, Garry
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
> Sent: Monday, 11 April 2011 10:51 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: Generating dummies with xi
>
> It is better to use factor variables directly than to use -xi:-.
>
> The only exception would be if are using an out-of-date version of
> Stata, say Stata 10, in which case you are asked to tell us that in the
> Statalist FAQ.
>
> That said, there seems to be some confusion here. First, -xi- will
> generate all pertinent dummies if asked directly. Second, a modelling
> command necessarily omits at least one such variable; that's the way
> that dummies work. Third, the help for -xi:- explains the use of
> -char- to get what you want, at least in Stata 10. (I don't have access
> to earlier versions at this time.)
>
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