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reshape2 is retired: only changes necessary to keep it on CRAN will be made. We recommend using tidyr instead.


Reshape2 is a reboot of the reshape package. It’s been over five years since the first release of reshape, 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 focused 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).