Can we see your data to be able to replicate the error? Or maybe a subset of data with some fake variable names?
On Tue, Apr 21, 2009 at 11:32 AM, Vemuri, Aparna <avem...@epri.com> wrote: > Yes, they are all of the same length. > > -----Original Message----- > From: Dimitri Liakhovitski [mailto:ld7...@gmail.com] > Sent: Tuesday, April 21, 2009 8:32 AM > To: Vemuri, Aparna > Cc: r-help@r-project.org > Subject: Re: [R] Fitting linear models > > Are they of the same length? > > On Tue, Apr 21, 2009 at 11:31 AM, Vemuri, Aparna <avem...@epri.com> wrote: >> The variables are all in separate vectors. >> >> -----Original Message----- >> From: Dimitri Liakhovitski [mailto:ld7...@gmail.com] >> Sent: Tuesday, April 21, 2009 8:26 AM >> To: Vemuri, Aparna >> Cc: David Winsemius; r-help@r-project.org >> Subject: Re: [R] Fitting linear models >> >> Aparna, >> >> I should have been more explicit. Run ?lm . You'll see this: >> >> "lm(formula, data, subset, weights, na.action, >> method = "qr", model = TRUE, x = FALSE, y = FALSE, qr = TRUE, >> singular.ok = TRUE, contrasts = NULL, offset, ...)" >> >> So, in addition to specifying the formula, you have to specify the >> data frame in which you keep your variables. I assume they are in a >> data frame? (unless for some reasons you keep all variables as >> separate vectors). >> So, after you wrote the formula, you have to indicate the name of the >> data frame, for example "MyData": >> >> model1<-lm(PBW~SO4+NO3+NH4, MyData) >> >> Dimitri >> >> On Tue, Apr 21, 2009 at 11:12 AM, Vemuri, Aparna <avem...@epri.com> wrote: >>> David, >>> Thanks for the suggestions. No, I did not label my dependent variable >>> "function". >>> >>> My dependent variable PBW and all the independent variables are continuous >>> variables. It is especially troubling since the order in which I input >>> independent variables determines whether or not it gets a coefficient. >>> Like I already mentioned, I checked the correlation matrix and picked the >>> variables with moderate to high correlation with the independent variable. >>> . So I guess it is not so naïve to expect a regression coefficient on all >>> of them. >>> >>> Dimitri >>> model1<-lm(PBW~SO4+NO3+NH4), gives me the same result as before. >>> >>> Bert: >>> This is not homework. But I will remember to do my research before posting >>> here. >>> >>> Aparna >>> >>> >>> -----Original Message----- >>> From: David Winsemius [mailto:dwinsem...@comcast.net] >>> Sent: Monday, April 20, 2009 5:35 PM >>> To: Vemuri, Aparna >>> Cc: r-help@r-project.org >>> Subject: Re: [R] Fitting linear models >>> >>> >>> On Apr 20, 2009, at 7:26 PM, Vemuri, Aparna 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. >>> >>> You can omit the unnecessary preambles. >>>> >>>> >>>> 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. >>> >>> You really did not name your dependent variable "function" did you? >>> Please stop that. >>> >>> Just a guess, ... since you have not provided enough information to do >>> otherwise, ... Are all of those variables 1/0 dummy variables? If so >>> and if you want to have an output that satisfies your need for >>> labeling the coefficients as you naively anticipate, then put "0+" at >>> the beginning of the formula or "-1" at the end, so that the intercept >>> will disappear and then all variables will get labeled as you expect. >>> >>> -- >>> David Winsemius, MD >>> Heritage Laboratories >>> West Hartford, CT >>> >>> ______________________________________________ >>> 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 >> > > > > -- > Dimitri Liakhovitski > MarketTools, Inc. > dimitri.liakhovit...@markettools.com > -- 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.
