~ a*b*d + a*c*d -- Bert On Thu, Sep 13, 2012 at 10:49 AM, Alexander Shenkin <ashen...@ufl.edu> wrote: > Hi Folks, > > I'm trying to find a way to remove all terms in a formula that contain a > particular interaction. > > For example, in the formula below, I'd like to remove all terms that > contain the b:c interaction. > >> attributes(terms( ~ a*b*c*d))$term.labels > [1] "a" "b" "c" "d" "a:b" "a:c" > [7] "b:c" "a:d" "b:d" "c:d" "a:b:c" "a:b:d" > [13] "a:c:d" "b:c:d" "a:b:c:d" > > My eventual use is to fit models with the reduced formulas. > > For example: >> my_df = data.frame( iv = runif(100), a=runif(100), b=runif(100), > c=runif(100), d=runif(100)) >> lm(iv ~ a*b*c*d, data=my_df) > > I can remove particular terms with update(), but I don't see a way to > remove all terms that contain a given combination of factors. > > Any help would be greatly appreciated. Thanks! > > Allie > > ______________________________________________ > 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.
