[R] different behavior of $ with string literal vs string variable as argument
bbolker at gmail.com
Sun Feb 10 22:58:59 CET 2013
Duncan Murdoch <murdoch.duncan <at> gmail.com> writes:
> On 13-02-10 4:06 PM, David Romano 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.
> You can use names with [[, e.g.
> will work in your example. You can see more details in the help topic
> help("$"), in the section "Recursive (list-like) objects".
> Duncan Murdoch
I nominate this issue as a candidate for an R FAQ entry. There's
at least one question on StackOverflow about it:
I think I've seen more but I can't find them right now (it's a little
hard to search on "$" and "[[") ...
More information about the R-help