[Rd] non-duplicate names in data frames

[Tim Hesterberg]

I wrote on another thread
(with subject "[ subscripting sometimes loses names"):
>I like R's 'automatic' row names.  This is a big help working with
>huge data frames (and I do this often, at Google).  But this doesn't
>go far enough; subscripting and other operations sometimes convert the
>automatic names to real names, and check/enforce uniqueness, which is
>a big waste of time when working with large data frames.  I'll comment
>more on this in a new thread.

I propose (and have begun writing, in my copious spare time):
* an optional argument to data.frame and other data frame creation code
* resulting in an attribute added to the data.frame
* so that subscripting and other operations on the data frame
  * always keep artificial row names
  * do not have to check for unique row names in the result.

My current thoughts, comments welcome:

Argument name and component name 'dup.row.names'
0 or FALSE or NULL - current, require unique names
1 or TRUE          - duplicates allowed (when subscripting etc.)
2                  - always automatic   (when subscripting etc.)

Option "maxRowNames", default say 10^4
Any data frames with more than this have dup.row.names default to 2.

The name 'dup.row.names' is for consistency with S+; there the options
are NULL, F or T.

Tim Hesterberg