Fair point. Thanks.
-----Original Message----- From: David Winsemius [mailto:dwinsem...@comcast.net] Sent: Friday, October 09, 2009 5:02 PM To: Brecknock, Peter Cc: Daniel Malter; r-help@r-project.org Subject: Re: [R] lm output On Oct 9, 2009, at 5:45 PM, Brecknock, Peter wrote: > Daniel > > Thanks very much for the reply. > > If the data fails the underlying assumptions of regression wouldn't > it make sense to suppress all the output and not just the slope > coefficient? > > Incidently, if I run this simple example in Excel it returns the > slope as 0. Intuitively, this makes sense to me ... the best > estimate of y would be its mean for any value of x. R gave you the best estimate for y. It was Excel that gave you an estimate for something for which it had no basis. There is no mean of dy/dx because dx=0. -- David. > > Kind regards > > Pete > > > -----Original Message----- > From: Daniel Malter [mailto:dan...@umd.edu] > Sent: Friday, October 09, 2009 4:24 PM > To: Brecknock, Peter; r-help@r-project.org > Subject: AW: [R] lm output > > That comes out as an NA because X'X is not invertible because it is > not full > rank (one row/column is a linear combination of the other(s)). And > that > means there is no unique solution to the system. > > y=c(10,12,17) > x=c(5,5,5) > X=cbind(1,x) > > X > t(X)%*%X > solve(t(X)%*%X) > > Therefore, nope, there is now way to make this come out as a zero, > because > it fails the very assumptions of regression analysis. > > HTH, > Daniel > > ------------------------- > cuncta stricte discussurus > ------------------------- > > -----Ursprüngliche Nachricht----- > Von: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] Im > Auftrag von Brecknock, Peter > Gesendet: Friday, October 09, 2009 5:12 PM > An: r-help@r-project.org > Betreff: [R] lm output > > Hi All > > I am running a linear regression using the lm object. > > In the event that my independent variable is the same across all > observations the regression slope is returned as an NA. > > For example, if I have the following > > y=c(10,12,17) > x=c(5,5,5) > > lm = lm(y~x) > produces the following > > Coefficients: > (Intercept) x > 13 NA > > Other than post-processing the results, is there a way to output the > slope > as 0 rather than NA? > > Thanks > > Pete > > > This e-mail may contain confidential or proprietary information > belonging to > the BP group and is intended only for the use of the recipients > named above. > If you are not the intended recipient, please immediately notify the > sender > and either delete this email or return to the sender immediately. > You may > not review, copy or distribute this email. Within the bounds of > law, this > part of BP retains all emails and IMs and may monitor them to ensure > compliance with BP's internal policies and for other legitimate > business > purposes. > > > [[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. 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.
