Try: model1<-lm(PBW~SO4+NO3+NH4) Does it work? Dimitri On Mon, Apr 20, 2009 at 7:26 PM, Vemuri, Aparna <avem...@epri.com> wrote: > I am not sure if this is an R-users question, but since most of you here > are statisticians, I decided to give it a shot. > > I am using the lm() function in R to fit a dependent variable to a set > of 3 to 5 independent variables. For this, I used the following > commands: > >>model1<-lm(function=PBW~SO4+NO3+NH4) > Coefficients: > (Intercept) SO4 NO3 NH4 > 0.01323 0.01968 0.01856 NA > > and > >>model2<-lm(function=PBW~SO4+NO3+NH4+Na+Cl) > > Coefficients: > (Intercept) SO4 NO3 NH4 > Na Cl > -0.0006987 -0.0119750 -0.0295042 0.0842989 0.1344751 > NA > > In both cases, the last independent variable has a coefficient of NA in > the result. I say last variable because, when I change the order of the > variables, the coefficient changes (see below). Can anyone point me to > the reason R behaves this way? Is there anyway for me to force R to use > all the variables? I checked the correlation matrices to makes sure > there is no orthogonality between the variables. > > Thanks > Aparna > > model1<-lm(formula = PBW ~ SO4 + NH4 +NO3) >> model1 > > Call: > lm(formula = PBW ~ SO4 + NH4 + NO3) > > Coefficients: > (Intercept) SO4 NH4 NO3 > 0.01323 -0.00430 0.06394 NA > > > > >> model2<-lm(formula = PBW ~ SO4 + NO3 + Na +Cl +NH4) >> model2 > > Call: > lm(formula = PBW ~ SO4 + NO3 + Na + Cl + NH4) > > Coefficients: > (Intercept) SO4 NO3 Na > Cl NH4 > -0.0006987 0.0196371 -0.0050303 0.0685020 0.0427431 > NA > > [[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. >
-- Dimitri Liakhovitski MarketTools, Inc. dimitri.liakhovit...@markettools.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.
