Great. Thank you! On Tue, May 29, 2012 at 8:11 AM, ONKELINX, Thierry <thierry.onkel...@inbo.be > wrote:
> offset() fixes the parameter to 1. So offset(I(.5*X2)) should do the trick. > > ir. Thierry Onkelinx > Instituut voor natuur- en bosonderzoek / Research Institute for Nature and > Forest > team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance > Kliniekstraat 25 > 1070 Anderlecht > Belgium > + 32 2 525 02 51 > + 32 54 43 61 85 > thierry.onkel...@inbo.be > www.inbo.be > > To call in the statistician after the experiment is done may be no more > than asking him to perform a post-mortem examination: he may be able to say > what the experiment died of. > ~ Sir Ronald Aylmer Fisher > > The plural of anecdote is not data. > ~ Roger Brinner > > The combination of some data and an aching desire for an answer does not > ensure that a reasonable answer can be extracted from a given body of data. > ~ John Tukey > > > -----Oorspronkelijk bericht----- > Van: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > Namens Dustin Fife > Verzonden: dinsdag 29 mei 2012 14:56 > Aan: Rui Barradas > CC: r-help > Onderwerp: Re: [R] setting parameters equal in lm > > That did it. Thanks! One more follow-up questions. How do I set a > parameter to a particular value? I tried I(.5*X2), but that didn't do what > I expected. > > On Tue, May 29, 2012 at 6:39 AM, Rui Barradas <ruipbarra...@sapo.pt> > wrote: > > > Hello, > > > > Your model is equivalent of > > > > y = b1(X1 + X3) + b2X2 > > > > (plus error) > > > > So, use I() to add X1 and X3. You don't need to create an extra > > variable > > X13 <- X1 + X3. See the help page for it. The point on function formula. > > > > ?I > > > > linMod2 = lm(Y ~ -1 + I(X1 + X3) + X2, data=data.set) > > summary(linMod2) > > # The same. > > linMod3 = lm(Y ~ 0 + I(X1 + X3) + X2, data=data.set) > > summary(linMod3) > > > > With set.seed(1) your common slope is > > > > coef(linMod2) > > I(X1 + X3) X2 > > 0.4237869 3.3626984 > > > > Also, I find it better to put 'library', 'require', etc as the first > > lines of code. > > > > Hope this helps, > > > > Rui Barradas > > > > Em 29-05-2012 04:14, Dustin Fife escreveu: > > > > Forgive me if this is a trivial question, but I couldn't find it an > > answer > >> in former forums. I'm trying to reproduce some SAS results where they > >> set two parameters equal. For example: > >> > >> y = b1X1 + b2X2 + b1X3 > >> > >> Notice that the variables X1 and X3 both have the same slope and the > >> intercept has been removed. How do I get an estimate of this > >> regression model? I know how to remove the intercept ("-1" somewhere > >> after the tilde). > >> But how about setting parameters equal? I have used the car package > >> to set up linear hypotheses: > >> > >> > >> X1 = rnorm(20, 10, 5); X2 = rnorm(20, 10, 5); X3 = rnorm(20, 10, 5) Y > >> = .5*X1 + 3*X2 + .5*X3 + rnorm(20, 0, 15) data.set = > >> data.frame(cbind(X1, X2, X3, Y)) linMod = lm(Y~X1 + X2 + X3, > >> data=data.set) > >> require(car) > >> linearHypothesis(linMod, c("(Intercept)=0", "X1-X3=0")) > >> > >> (forgive the unconventional use of the equal sign....old habit). > >> Unfortunately, the linearHypothesis is always compared to a full > >> model (where the parameters are freely estimated). I want to have an > >> ANOVA summary table for the reduced model. Any ideas? Thanks in > >> advance for the help! > >> > >> > > > -- > Dustin Fife > PhD Student > Quantitative Psychology > University of Oklahoma > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > * * * * * * * * * * * * * D I S C L A I M E R * * * * * * * * * * * * * > Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver > weer en binden het INBO onder geen enkel beding, zolang dit bericht niet > bevestigd is door een geldig ondertekend document. > The views expressed in this message and any annex are purely those of the > writer and may not be regarded as stating an official position of INBO, as > long as the message is not confirmed by a duly signed document. > -- Dustin Fife PhD Student Quantitative Psychology University of Oklahoma [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
