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st: RE: RE: xi regress: noconstant option
Original was beheaded, but I can spare this line.
Original was beheaded, so perhaps the above will be too.
> -----Original Message-----
> From: firstname.lastname@example.org
> [mailto:email@example.com]On Behalf Of Nick Cox
> Sent: 14 February 2005 15:45
> To: firstname.lastname@example.org
> Subject: st: RE: xi regress: noconstant option
---> . xi : regress return country
> does nothing different from
> regress return country
> so perhaps you mean
> xi : regress return i.country
> The latter model just fits
> the means of return for each country.
> It is essentially an alternative to
> Adding the -nocons- option just
> forces the mean for the first country,
> or more generally the category omitted,
> to 0 and leaves the other predictions
> unchanged. I can't think of a scientific
> or statistical reason to do that, but
> that may be failure of imagination
> or just plain ignorance on my part.
> More generally, the rationale for
> forcing through the origin is usually
> something like a law of physics
> which tells you that the relationship
> really should start there. Doesn't
> sound like your case.
> Yvonne Capstick
> > I have two categories: "return" and "country", where return
> > is "numeric" and
> > "country" is a three letter code corresponding to the
> > country. I know that I
> > can use the "xi" function to create dummy variables and run
> > the regressions
> > all in one step, i.e.
> > xi : regress return country
> > To avoid the dummy variable trap, it automatically omits the
> > first group of
> > "country". I know that I can use the "char" function to
> > specify omitting
> > another group, e.g.
> > char country[omit] "ita"
> > would omit the group "ita".
> > However, I haven't found a way to omit no groups - i.e.
> > include all the
> > dummy variables, and avoid the dummy variable trap by specifying
> > "noconstant" in the regression. If I try:
> > xi: regress return country, noconstant
> > it will omit the constant but still omit the first group of
> > "country". Any
> > advice would be appreciated.
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