Please read the Help before posting. ?"$" says:
"Both [[ and $ select a single element of the list. The main difference is that $ **does not allow computed indices** , whereas [[ does. x$name is equivalent to x[["name", exact = FALSE]]. Also, the partial matching behavior of [[ can be controlled using the exact argument. " [emphasis added] In other words, $ does not evaluate its argument. This also appeared just a couple of days ago on this list, so please also search Help archives before posting. -- Bert On Sun, Feb 10, 2013 at 1:06 PM, David Romano <drom...@stanford.edu> wrote: > Hi everyone, > > I ran into the issue below while trying to execute a command of the form > > apply(list.names,1, function(x) F(favorite.list$x) ) > > where list.names is a character vector containing the names of the elements > of favorite.list and F is some function defined on a list element. > > Namely, the $ operator doesn't treat the string variable 'x' as the string > it represents, so that, e.g. > >> ll <- list(ss="abc") >> ll$ss > [1] "abc" >> ll$"ss" > [1] "abc" > > but > >> name <- "ss" >> ll$name > NULL > > I can get around this by using integers and the [[ and [ operators, but I'd > like to be able to use names directly, too -- how would I go about doing > this? > > Thanks for your help in clarifying what might be going on here. > > David > > [[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.
