[Rd] Extract.data.frame.Rd about $.data.frame

[Suharto Anggono Suharto Anggono]

In R devel, data.frame method of '$' has been removed, but this part of "Details" section of Extract.data.frame.Rd still implies existence of the method.

  The \code{data.frame} method for \code{$}, treats \code{x} as a
  list, except that (as of R-3.1.0) partial matching of \code{name} to
  the names of \code{x} will generate a warning; this may become an
  error in future versions.  The replacement method checks
  \code{value} for the correct number of rows, and replicates it if
  necessary.


Statement from before R 3.1.0 could be used again:

  There is no \code{data.frame} method for \code{$}, so \code{x$name}
  uses the default method which treats \code{x} as a list.  There is a
  replacement method which checks \code{value} for the correct number
  of rows, and replicates it if necessary.