hits=-2.6 tests=BAYES_00 X-USF-Spam-Flag: NO On Thu, 2008-02-07 at 11:56 +0100, Falco tinnunculus wrote: > Hi, > > How do I calculate normality distribution of the residuals from a test in R? > > I have tried plot(mod1), and I get a nice plot, but no p-value... is there > some other ways to calculate this? > > Regards Kes,
You could use a QQ-plot to judge normality of residuals. x <- runif(100) y <- 3 + (0.8 * x) + rnorm(100, mean = 0, sd = 0.5) mod <- lm(y ~ x) mod.resi <- resid(mod) qqnorm(mod.resi) qqline(mod.resi) Systematic deviations from the line, indicate departures from normality (in this case), such as heavy tails, skewness. If the residuals were normally distributed they should be scattered around the line. G -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ [email protected] 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.
