Yep that's exactly right! :) On Mon, Mar 25, 2013 at 6:22 PM, Antonio P. Ramos <ramos.grad.stud...@gmail.com> wrote: > Just to clarify: I should include wealth - the categorical variable - as a > fixed effects *and* within the smooth using the argument "by". It that > correct? thanks a bunch > > > On Mon, Mar 25, 2013 at 6:18 PM, Joshua Wiley <jwiley.ps...@gmail.com> > wrote: >> >> Hi Antonio, >> >> If wealth is a factor variable, you should include the main effect in >> the model, as the smooths will be centered. >> >> Cheers, >> >> Josh >> >> >> >> On Mon, Mar 25, 2013 at 6:09 PM, Antonio P. Ramos >> <ramos.grad.stud...@gmail.com> wrote: >> > Hi all, >> > >> > I am not sure how to handle interactions with categorical predictors in >> > the >> > GAM models. For example what is the different between these bellow two >> > models. Tests are indicating that they are different but their >> > predictions >> > are essentially the same. >> > >> > Thanks a bunch, >> > >> >> gam.1 <- gam(mortality.under.2~ maternal_age_c+ I(maternal_age_c^2)+ >> > + s(birth_year,by=wealth) + >> > + + wealth + sex + >> > + residence+ maternal_educ + birth_order, >> > + ,data=rwanda2,family="binomial") >> >> >> >> gam.2 <- gam(mortality.under.2~ maternal_age_c+ I(maternal_age_c^2)+ >> > + s(birth_year,by=wealth) + >> > + + sex + >> > + residence+ maternal_educ + birth_order, >> > + ,data=rwanda2,family="binomial") >> >> >> >> anova(gam.1,gam.2,test="Chi") >> > Analysis of Deviance Table >> > >> > Model 1: mortality.under.2 ~ maternal_age_c + I(maternal_age_c^2) + >> > s(birth_year, >> > by = wealth) + +wealth + sex + residence + maternal_educ + >> > birth_order >> > Model 2: mortality.under.2 ~ maternal_age_c + I(maternal_age_c^2) + >> > s(birth_year, >> > by = wealth) + +sex + residence + maternal_educ + birth_order >> > Resid. Df Resid. Dev Df Deviance Pr(>Chi) >> > 1 28986 24175 >> > 2 28989 24196 -3.6952 -21.378 0.0001938 *** >> > --- >> > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 >> >> str(rwanda2) >> > 'data.frame': 29027 obs. of 18 variables: >> > $ CASEID : Factor w/ 10718 levels " 1 5 2",..: 289 >> > 2243 7475 9982 6689 10137 7426 428 8415 10426 ... >> > $ mortality.under.2 : int 0 1 0 0 0 0 0 0 1 0 ... >> > $ maternal_age_disct: Factor w/ 3 levels "-25","+35","25-35": 1 1 1 1 1 >> > 1 >> > 3 1 3 1 ... >> > $ maternal_age : int 18 21 21 23 21 22 26 18 27 21 ... >> > $ time : int 3 3 3 3 3 3 3 3 3 3 ... >> > $ child_mortality : num 0.232 0.232 0.232 0.232 0.232 ... >> > $ democracy : Factor w/ 1 level "dictatorship": 1 1 1 1 1 1 1 1 >> > 1 >> > 1 ... >> > $ wealth : Factor w/ 5 levels "Lowest quintile",..: 2 4 1 4 >> > 5 1 >> > 4 1 4 5 ... >> > $ birth_year : int 1970 1970 1970 1970 1970 1970 1970 1970 1970 >> > 1970 ... >> > $ residence : Factor w/ 2 levels "Rural","Urban": 1 1 1 1 2 1 1 >> > 1 >> > 1 2 ... >> > $ birth_order : int 1 2 2 5 1 1 3 1 2 2 ... >> > $ maternal_educ : Factor w/ 4 levels "Higher","No education",..: 3 >> > 2 2 >> > 3 4 2 3 2 2 2 ... >> > $ sex : Factor w/ 2 levels "Female","Male": 1 1 2 2 1 1 2 >> > 2 >> > 2 2 ... >> > $ quinquennium : Factor w/ 7 levels "00-5's","70-4",..: 2 2 2 2 2 >> > 2 2 >> > 2 2 2 ... >> > $ time.1 : int 3 3 3 3 3 3 3 3 3 3 ... >> > $ new_time : int 0 0 0 0 0 0 0 0 0 0 ... >> > $ maternal_age_c : num -6.12 -3.12 -3.12 -1.12 -3.12 ... >> > $ birth_year_c : num -14.8 -14.8 -14.8 -14.8 -14.8 ... >> > >> > [[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. >> > >> >> >> >> -- >> Joshua Wiley >> Ph.D. Student, Health Psychology >> University of California, Los Angeles >> http://joshuawiley.com/ >> Senior Analyst - Elkhart Group Ltd. >> http://elkhartgroup.com > >
-- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://joshuawiley.com/ Senior Analyst - Elkhart Group Ltd. http://elkhartgroup.com ______________________________________________ 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.
