Dear Miles, Within rounding error, you got the right intercept, log(3); slope, 0; residuals, all 0; residual standard error, 0; and standard errors of the intercept and slope, both 0. The R^2 should have been undefined (i.e., 0/0), but dividing one number that's 0 within rounding error by another gives a wild result. Likewise for the omnibus F and t-test for the slope. The moral: don't expect floating-point arithmetic on a computer to be perfectly precise.
I hope this helps, John -------------------------------- John Fox Senator William McMaster Professor of Social Statistics Department of Sociology McMaster University Hamilton, Ontario, Canada http://socserv.mcmaster.ca/jfox > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Miles Yang > Sent: November-14-11 10:49 PM > To: r-help-requ...@r-project.org; r-help@r-project.org > Subject: [R] Question about linear regression in R > > Hi all, > I wrote a r program as below: > > x <- 1:10 > y <- c(3,3,3,3,3,3,3,3,3,3) > > fit <- lm(log(y) ~ x) > summary(fit) > > And I expect to get some error message from R, because "y" is constant. > But, I got the message as below: > > > summary(fit) > > Call: > lm(formula = log(y) ~ x) > > Residuals: > Min 1Q Median 3Q Max > -6.802e-17 -3.933e-17 -1.063e-17 1.807e-17 1.530e-16 > > Coefficients: > Estimate Std. Error t value Pr(>|t|) > (Intercept) 1.099e+00 4.569e-17 2.404e+16 <2e-16 *** > x -1.275e-17 7.364e-18 -1.732e+00 0.122 > --- > Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 > > Residual standard error: 6.688e-17 on 8 degrees of freedom Multiple R- > squared: 0.5794, Adjusted R-squared: 0.5269 > F-statistic: 11.02 on 1 and 8 DF, p-value: 0.01054 > > How could this be possible? > Did I missing something in my R code? > > Best, > Miles > -- > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o<Miles Yang > Mobileo<+61-411-985-538 > E-mailo<miles2y...@gmail.com > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > o< > [[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.
