When I run a linear regression and include a variable in the regression with as.factor i.e. lm(y ~x +as.factor(x1) and i read the output as as.factor(x1)1.... as.factor(x1)2... etc. how do i interpret the estimate for each level? Is this simply to be regarded as a shift in the equation predicted by the intercept and independent variable x? jdr -- Justin Rapp 409 S. 22nd St. Apt. 1 Philadelphia, PA 19146 Cell:(267)252.0297
Un texte encapsul? et encod? dans un jeu de caract?res inconnu a ?t? nettoy?... Nom : non disponible Url : https://stat.ethz.ch/pipermail/r-help/attachments/20060623/dea4a922/attachment.pl
probably you want to look at the help page of ?contr.treatment
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
Quoting Justin Rapp <justin.rapp at gmail.com>:
> When I run a linear regression and include a variable in the
> regression with as.factor i.e.
>
> lm(y ~x +as.factor(x1)
>
> and i read the output as
> as.factor(x1)1....
> as.factor(x1)2...
> etc.
>
> how do i interpret the estimate for each level? Is this simply to
> be
> regarded as a shift in the equation predicted by the intercept and
> independent variable x?
>
> jdr
>
>
> --
> Justin Rapp
> 409 S. 22nd St.
> Apt. 1
> Philadelphia, PA 19146
> Cell:(267)252.0297
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>
>
Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
Try this: model.matrix(y ~ x + as.factor(x1)) to see the model matrix that is being used. Matrix multiplication of that matrix by the coefficients is the prediction equation. On 6/23/06, Justin Rapp <justin.rapp at gmail.com> wrote:> When I run a linear regression and include a variable in the > regression with as.factor i.e. > > lm(y ~x +as.factor(x1) > > and i read the output as > as.factor(x1)1.... > as.factor(x1)2... > etc. > > how do i interpret the estimate for each level? Is this simply to be > regarded as a shift in the equation predicted by the intercept and > independent variable x? > > jdr > > > -- > Justin Rapp > 409 S. 22nd St. > Apt. 1 > Philadelphia, PA 19146 > Cell:(267)252.0297 > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html >