Sorry, this was meant to go to the full list. -David On Sun, Feb 10, 2013 at 2:15 PM, David Romano <drom...@stanford.edu> wrote:
> > > On Sun, Feb 10, 2013 at 1:59 PM, Bert Gunter <gunter.ber...@gene.com>wrote: > >> Please read the Help before posting. >> >> ?"$" says: >> > > It helps to know that $ must be quoted, so thanks again goes to Duncan for > pointing this out. > > >> "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. >> > > I did search, but as Ben points out in the next message in the thread, > it's tricky to formulate the search to get hits, and, for example, I > wouldn't have realized the post he refers to there involves the same issue > unless I already knew the answer. > > David > > -- 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 >> > > [[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.
