This is answered in ?AIC. Have you read it? -- Bert
On Mon, Feb 13, 2012 at 10:22 AM, david hamer <j.david.ha...@gmail.com> wrote: > Using the Cement hardening data in Anderson (2008) Model Based Inference in > the Life Sciences. A Primer on Evidence, and working with the best model > which is > lm ( y ~ x1 + x2, data = cement ) > the AIC value from R is > > model <- lm ( formula = y ~ x1 + x2 , data = > cement ) > AIC ( model ) > > 64.312 > > which can be converted to AICc by adding the bias correction factor > 2*K*(K+1)/(n-K-1) to give the AICc value of > 69.312 > (addition of 5, where n=13 and K=4). > > This same value, 69.31, can be obtained using R package > AICcmodavg > > library ( AICcmodavg ) > data (cement) > cement > Cand.models <- list( ) > Cand.models[[1]] <- lm ( y ~ x1 + x2, data = cement ) > Cand.models[[2]] <- lm ( y ~ x3 + x4, data = cement ) > Cand.models[[3]] <- lm ( y ~ x1 + x2 + x1 * x2, data = > cement ) > Cand.models[[4]] <- lm ( y ~ x3 + x4 + x3 * x4, data = > cement ) > ## vector of model names > Modnames <- paste("MODEL", 1:4, sep=" ") > ## AICc > aictab ( cand.set = Cand.models, modnames = Modnames ) > > However, the AICc value reported by Anderson (2008) is > 32.41. > The AICc value obtained using RSS value (i.e., calculating AICc "manually" > from the output of linear regression) is > 32.41. > > Thanks for any help. > David > New R user, minimal familiarity with statistics. > > [[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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.