Dear Ista! Thank you for replying. The point you made is exactly what's the problem: I want to predict the values at different points in space. calP stands for the water content at each sampling point (n=90) but I don't quite understand what R does. calP is my vector of measured data and I thought with the predict function the programm would calculate a value from the model function for every value of calP... ?
2011/3/20 Ista Zahn <iz...@psych.rochester.edu>: > Hi Anna, > > On Sun, Mar 20, 2011 at 2:54 PM, Anna Lee <ana-...@web.de> wrote: >> Hey List, >> >> I did a multiple regression and my final model looks as follows: >> >> model9<-lm(calP ~ nsP + I(st^2) + distPr + I(distPr^2)) >> >> Now I tried to predict the values for calP from this model using the >> following function: >> >> xv<-seq(0,89,by=1) >> yv<-predict(model9,list(distPr=xv,st=xv,nsP=xv)) > > The second argument to predict.lm is newdata, which should be a > data.frame. see ?predict.lm. > > Beyond that though, I'm not sure what you are trying to accomplish. > The way you've set this up you would get predicted values for cases > like > > distPr st nsp > 0 0 0 > 1 1 1 > 2 2 2 > . . . > 89 89 89 > > > Is that really what you want? > > Best, > Ista >> >> The predicted values are however strange. Now I do not know weather >> just the model does not fit the data (actually all coefficiets are >> significant and the plot(model) shows a good shape) or wether I did >> something wrong with my prediction command. Does anyone have an >> idea??? >> >> -- >> >> >> Thanks a lot, Anna >> >> ______________________________________________ >> 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. >> > > > > -- > Ista Zahn > Graduate student > University of Rochester > Department of Clinical and Social Psychology > http://yourpsyche.org > -- Der Inhalt dieser E-Mail ist vertraulich. Sollte Ihnen die E-Mail irrtümlich zugesandt worden sein, bitte ich Sie, mich unverzüglich zu benachrichtigen und die E-Mail zu löschen. This e-mail is confidential. If you have received it in error, please notify me immediately and delete it from your system. ______________________________________________ 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.