[Rd] data frame subset patch, take 2

[Marcus G. Daniels]

Vladimir Dergachev wrote:

>     2. It would be nice to have true hashed arrays in R (i.e. O(1) access 
> times). So far I have used named lists for this, but they are O(n):
>   
new.env(hash=TRUE) with get/assign/exists works ok.  But I suspect its 
just too easy to use named lists because it is easy, and that has bad 
performance ramifications for user code (perhaps the R developers are 
more vigilant about this for the R code itself).