On Wed, 6 Aug 2008, Faheem Mitha wrote:
Hi,
Consider the following
x = c(1,2)
y = c(3,4)
d = data.frame(cbind(x,y))
d$x
[1] 1 2
d$"x"
[1] 1 2
foo = function(val)
+ {
+ return(d$val)
+ }
bar = function()
+ {
+ return(d$"x")
+ }
foo("x")
NULL
bar()
[1] 1 2
I'm a little surprised that R accepts both the form d$x and d$"x", but I'm
mostly wondering why foo("x") doesn't work.
It does work: it returns d$val as instructed. From the help
Usage:
x$name
name: A literal character string or a name (possibly backtick
quoted).
or see the version in ?`$.data.frame`.
So you are 'a little surprised' that the function works as described on
the help page! Please explain to us how you can to that conclusion.
I think you are looking for [[ (on the same help page as $).
Thanks, Faheem.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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