Here is one way: > fo <- y ~ f1 * f2 > one.x <- lapply(all.vars(fo[[3]]), function(x) { fo[[3]] <- as.name(x); fo }) > one.x [[1]] y ~ f1
[[2]] y ~ f2 On Wed, Oct 21, 2009 at 11:29 AM, Bryan Hanson <han...@depauw.edu> wrote: > Hello All.. > > Please consider the following: > > y <- rnorm(20, mean = 10) > f1 <- as.factor(rep(c("A", "B", "B", "A"), 5)) > f2 <- as.factor(rep(c("C", "D"), 10)) > testdata <- data.frame(y, f1, f2) > > testFunc <- function(formula, data, ...) { > # mf <- model.frame(formula, data) > kw.res <- kruskal.test(formula, data) > } > > res <- testFunc(y ~ f1 * f2, testdata) > > Which works perfectly well. Now, I would like to do some other tests which > allow only one factor, for instance wilcox.test. So, I would like to modify > my formula so that it reads y ~ f1 or y ~ f2, then conduct more tests. What > is the smart way to subset or modify an existing symbolic formula? I have > been staring at the attributes of res and mf (commented out currently) but > these are nested in a way I find difficult to extract. ?terms, > ?terms.formula, ?formula etc all discuss these attributes but as I said, it > seems a bit impenetrable. RSiteSearch("symbolic formula") returns too many > answers. No doubt I am missing the obvious, as this is my first foray into > using formulas in my own functions. > > TIA, Bryan > ************* > Bryan Hanson > Acting Chair > Professor of Chemistry & Biochemistry > DePauw University, Greencastle IN USA > > >> sessionInfo() > R version 2.10.0 RC (2009-10-19 r50172) > i386-apple-darwin8.11.1 > > locale: > [1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8 > > attached base packages: > [1] datasets tools grid utils stats graphics grDevices > methods > [9] base > > other attached packages: > [1] ggplot2_0.8.3 reshape_0.8.3 proto_0.3-8 mvbutils_2.2.0 > [5] ChemoSpec_1.2 lattice_0.17-25 mvoutlier_1.4 plyr_0.1.8 > [9] RColorBrewer_1.0-2 chemometrics_0.4 som_0.3-4 > robustbase_0.4-5 > [13] rpart_3.1-45 pls_2.1-0 pcaPP_1.7 mvtnorm_0.9-7 > [17] nnet_7.2-48 mclust_3.2 MASS_7.2-48 lars_0.9-7 > [21] e1071_1.5-19 class_7.2-48 > > ______________________________________________ > 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. > ______________________________________________ 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.