[R-Forge #2175] Add natural joins i.e. X[Y] when X has no key could use common column names

[arunsrinivasan]

Submitted by: Matt Dowle; Assigned to: Nobody; R-Forge link

Use matching column names in this case.

As suggested by David Kulp here :

http://lists.r-forge.r-project.org/pipermail/datatable-help/2012-August/001241.html

Or, leave this to merge (since merge.data.table does that)? And if so, document.

[MichaelChirico]

This is easy now with on, correct? could set default of on to intersect(names(dt1),names(dt2)), for example.

[franknarf1]

@MichaelChirico I would prefer to see a special value for on (similar to .EACHI), to keep it explicit/transparent, like on=.COMMON.

While we're at it, I suppose there could be an onby (if the logic & code are structured so that that actually makes sense).

[MichaelChirico]

This seems like a close relative of the recently-closed #1517

[MichaelChirico]

@franknarf1 in keeping with SQL-inspired syntax, I was thinking on = .NATURAL would be a very natural (sorry) way to implement this.