> What I wondered is if I pass the 'upper=~.' , > it seems step() thinks the full model is current one. Not adding > anymore. If this is the right answer, is there a better way than > creating fmla argument in the above?
Yes, that is exactly what the help page for step says it means. (So why are you unsure and asking?) upper = terms(Response ~ ., data=ds3)) would appear to be a simpler way to get your intention. On Fri, 1 Jul 2005, Young Cho wrote: > Thanks a lot for help in advance. I am switching from matlab to R and I > guess I need some time to get rolling. I was wondering why this code : > >> fit.0 <- lm( Response ~ 1, data = ds3) >> step(fit.0,scope=list(upper=~.,lower=~1),data=ds3) > Start: AIC= -32.66 > Response ~ 1 > > Call: > lm(formula = Response ~ 1, data = ds3) > Coefficients: > (Intercept) > 1.301 > > > is not working different from the following: > >> >> cnames <- dimnames(ds3)[[2]] >> cnames <- cnames[-444] # last col is Response >> >> fmla <- as.formula(paste(" ~ ",paste(cnames,collapse="+"))) >> step(fit.0,scope=list(upper=fmla,lower=~1),data=ds3) > Start: AIC= -32.66 > Response ~ 1 >> fmla <- as.formula(paste(" ~ ",paste(cnames,collapse="+"))) >> fit.s <- step(fit.0,scope=list(upper=fmla,lower=~1),data=ds3) > > Step: AIC= -Inf > Response ~ ENTP9324 + CH1W0281 > Df Sum of Sq RSS AIC > <none> 0 -Inf > - CH1W0281 3 0.00381 0.00381 -115 > - ENTP9324 9 1 1 -34 > > The dataframe ds3 is 17 by 444 and I understand it is not smart thing to > run stepwise regression. What I wondered is if I pass the 'upper=~.' , > it seems step() thinks the full model is current one. Not adding > anymore. If this is the right answer, is there a better way than > creating fmla argument in the above? -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help@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