# predicting values from multiple regression

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## predicting values from multiple regression

 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 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 ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: predicting values from multiple regression

 Hi Anna, On Sun, Mar 20, 2011 at 2:54 PM, Anna Lee <[hidden email]> 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 > > ______________________________________________ > [hidden email] 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______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: predicting values from multiple regression

 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 <[hidden email]>: > Hi Anna, > > On Sun, Mar 20, 2011 at 2:54 PM, Anna Lee <[hidden email]> 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 >> >> ______________________________________________ >> [hidden email] 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. ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: predicting values from multiple regression

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