Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: RE: RE: xi regress: noconstant option


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: xi regress: noconstant option
Date   Mon, 14 Feb 2005 15:48:36 -0000

Original was beheaded, but I can spare this line. 
Original was beheaded, so perhaps the above will be too. 

Nick 
n.j.cox@durham.ac.uk 

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Nick Cox
> Sent: 14 February 2005 15:45
> To: statalist@hsphsun2.harvard.edu
> 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 
> -anova-. 
> 
> 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. 
> 
> Nick 
> n.j.cox@durham.ac.uk 
> 
> 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.
> 
> *
> *   For searches and help try:
> *   http://www.stata.com/support/faqs/res/findit.html
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
> 

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index