No, actually it does better to not suppress all output, because it tells you where the trouble comes from by just showing the NA for the slope. The intercept the regression gives you is the mean of y in this case. As for the slope, Ted's graphic is illustrative as to why no slope can be estimated. Overall, I would say the output makes sense.
Daniel ------------------------- cuncta stricte discussurus ------------------------- -----Ursprüngliche Nachricht----- Von: Brecknock, Peter [mailto:peter.breckn...@bp.com] Gesendet: Friday, October 09, 2009 5:45 PM An: Daniel Malter; r-help@r-project.org Betreff: RE: [R] lm output 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. 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.
