Reshape2 is a reboot of the reshape package. It's been over five years since the first release of the package, and in that time I've learned a tremendous amount about R programming, and how to work with data in R. Reshape2 uses that knowledge to make a new package for reshaping data that is much more focussed and much much faster.

This version improves speed at the cost of functionality, so I have renamed it to reshape2 to avoid causing problems for existing users. Based on user feedback I may reintroduce some of these features.

What's new in reshape2:

Initial benchmarking has shown melt to be up to 10x faster, pure reshaping cast up to 100x faster, and aggregating cast() up to 10x faster.

This work has been generously supported by BD (Becton Dickinson).