[R-Forge #2033] Add by.x and by.y to merge.data.table

[arunsrinivasan]

Submitted by: Chris Neff; Assigned to: Nobody; R-Forge link

Especially implementing by.x and by.y.

[ctbrown]

For what it is worth, I have been bitten by the lack of by.x / by.y more then once.

[gcdnyc]

i am actually moving back to using data frames instead of data tables since i need to use merge frequently, and work with lots of datasets with different column names. hopefully this will be enhanced soon, although i see this post from Matt from 3 years ago about this topic:

http://stackoverflow.com/questions/14069796/merging-data-tables-based-on-columns-names

[jangorecki]

@gcdnyc a simple wrapper to re-setkey on columns which has to be joined seems to be pretty straightforward to handle that.
There are multiple functionalities which are easy do-able in data.table, just not wrapped as single call, see set operators, cross join. Some PR with those functions are waiting here on github. I believe Matt and Arun wants to incorporate them in the most efficient way with good docs and tests.
If you would develop such wrapper you may drop a link here so others may use/contribute to it.