[R-Forge #2185] Add features/documentation for sliding windows with data.table

[arunsrinivasan]

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

As asked here:

but in that question data.table already seems much faster (6.4s) than the alternative (973s).

Should be just documenting (including timings) how to use good sliding window functions with data.table, rather than any new functionality per se.

[jangorecki]

Looking forward for the update of documentation to extend previously prepared benchmark of sliding window (with variable window width) for data.table solution, benchmark available here: http://stackoverflow.com/a/21368246/2490497

[jangorecki]

closing as duplicate of #2778