Hi Greg Thanks for responding. When I scale stackloss and compute the fitted values of the scaled data frame, the values are not the same: A<-data.frame(scale(stackloss))
lm<- lm(stack.loss ~ . -1, qr=T, data=A) summary(lm) fitted.values(lm) Or should I not be comparing the two? >>> Greg Snow <greg.s...@imail.org> 2009/02/19 07:31 PM >>> You are computing the hat matrix to predict stack.loss, but stack.loss is a column in the A matrix, so you predictions are all perfect (given stack.loss, what is stack.loss, fairly simple answer, all errors are 0). I think you want to redo this using only the 3 columns other than stack.loss in the call to svd, then you should get the results that you are expecting. Hope this helps, -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of Kutlwano Ramaboa > Sent: Wednesday, February 18, 2009 10:43 PM > To: r-help@r-project.org > Subject: [R] matrix computation??? > > Hello > > Can anyone tell me what I am doing wrong below? My Y and y_hat are the > same. > > > > A<-scale(stackloss) > n1<- dim(A)[1];n2<-dim(A)[2] > X<-svd(A) > Y<- matrix(A[,"stack.loss"],nrow=n1) > Y > y_hat <-matrix((X$u%*% t(X$u))%*%Y,nrow=n1,byrow=T) > y_hat > > [[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. ______________________________________________ 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. [[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.
