[R] What does m$... mean?

[Spencer Graves]

"a$b" = "a[['b']] = attribute "b" of list "a".

A basic object in R is a list, and the "$" operator provides one means 
of accessing named attributes of a list.

	  Beginning with R 1.7, objects can also have "slots", which are 
accessed as "a at b".  I have yet to understand why "slots" were 
introduced;  perhaps someone else will explain this.

hope this helps.
spencer graves

Richard A. O'Keefe wrote:
> While reading through some of the R source code, I have come
> across forms such as
>     m$...
>     m$... <- e
> and I wondered what they meant.
> 
> ?"$" mentions x$name, but not $... 
> All it says is
> 
>      The operators `$' and `$<-' do not evaluate their second argument.
>       It is translated to a string and that string is used to locate
>      the correct component of the first argument.
> 
> Does this mean that m$... is the same as m$"..."
> and m$... <- e is the same as m$"..." <- e?
> 
> That's what it seems to do when I try it on some small data frames,
> but is that ALL there is to it, or is there some special magic going
> on?  Is there any connection with the use of ... in formal and actual
> parameter lists, or is it just accidental?  Why would anyone _want_
> to use $... ?
> 
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