reshape2 1.4 is now available on CRAN. This version adds a number of useful arguments and messages, but mostly importantly it gains a C++ implementation of
melt.data.frame(). This new method should be much much faster (>10x) and does a better job of preserving existing attributes. For full details, see the release notes on github.
The C++ implementation of melt was contributed by Kevin Ushey, who we’re very pleased to announce has joined RStudio. You may be familiar with Kevin from his contributions to Rcpp, or his CRAN packages Kmisc and timeit.