Hi, Your X'X matrix is singular and there is not a unique solution. If you check, the regression equation which R gave you works just as well as yours. This is because your predictor variables are perfectly dependent. This will essentially never happen with real applications do to measurement errors.
Jonathan On Fri, Jul 30, 2010 at 9:07 AM, Ambikesh Jayal <ambi1...@gmail.com> wrote: > Hi, > > Subject: Using R for Multiple Regression > > I am new to statistic but am interested in applying mathematical models to > solve biological problems. I have used a linear model to generate the test > data. When using this data I expect R to correctly identify the model but > that does not seem to be the case. I am certain that I am doing something > wrong but not able to figure it out. > > Model: > Y = m1x1 + m2x2+ m3X3 + c > > m1=5 > m2=6 > m3=0 > c=2 > > Model Identified by R using lm(formula = y ~ x1 + x2 + x3) > (Intercept) 8.000e+01 > x1 1.100e+01 > x2 NA > x3 NA > > > The data I am using is as follows: > > y x1 x2 x3 > 91 1 14 2 > 102 2 15 5 > 113 3 16 8 > 124 4 17 11 > 135 5 18 14 > 146 6 19 17 > 157 7 20 20 > 168 8 21 23 > 179 9 22 26 > 190 10 23 29 > > Kind regards > > Dr. Ambikesh Jayal, > Department of Information Systems, Computing and Mathematics > Room 134 St John's Building > Brunel University > Uxbridge, Middlesex > UB8 3PH, UK > Website: http://sites.google.com/site/ambi1999/ > > [[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. > [[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.
