Dear All, I'm hoping one of you can help me with the following R problem. I'm trying to refer to a member of a list by variable. However, this seems not to work: foo=list(first=c(1:10),second=c(11:20))> foo$first[1] 1 2 3 4 5 6 7 8 9 10> foo$"first"[1] 1 2 3 4 5 6 7 8 9 10> goo=c("first")> foo$gooNULL> foo$goo[1]NULL I'm sure I'm missing something quite elementary. Perhaps you can help? RR
On Mon, 2008-12-01 at 10:53 -0800, Reitsma, Rene - COB wrote:> Dear All, > > I'm hoping one of you can help me with the following R problem. I'm > trying to refer to a member of a list by variable. However, this seems > not to work: > > foo=list(first=c(1:10),second=c(11:20)) > > > foo$first > [1] 1 2 3 4 5 6 7 8 9 10 > > > foo$"first" > [1] 1 2 3 4 5 6 7 8 9 10 > > > goo=c("first") > > > foo$goo > NULLfoo[[goo]] See ?`[[` for more details. Not sure if there is an incantation that will work with '$' in this case. HTH G> > > foo$goo[1] > NULL > > I'm sure I'm missing something quite elementary. Perhaps you can help? > > RR > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.
On Mon, Dec 1, 2008 at 12:53 PM, Reitsma, Rene - COB <reitsmar at bus.oregonstate.edu> wrote:> Dear All, > > I'm hoping one of you can help me with the following R problem. I'm > trying to refer to a member of a list by variable. However, this seems > not to work: > > foo=list(first=c(1:10),second=c(11:20)) > >> foo$first > [1] 1 2 3 4 5 6 7 8 9 10 > >> foo$"first" > [1] 1 2 3 4 5 6 7 8 9 10 > >> goo=c("first") > >> foo$goo > NULL > >> foo$goo[1] > NULL >foo[[goo]] which you'll find in ?"$" under the heading "Recursive (list-like) objects" Hadley -- http://had.co.nz/