Flexibly Reshape Data: A Reboot of the Reshape Package.
reshape2
Status
reshape2 is retired: only changes necessary to keep it on CRAN will be made. We recommend using tidyr instead.
Introduction
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
:
considerably faster and more memory efficient thanks to a much better underlying algorithm that uses the power and speed of subsetting to the fullest extent, in most cases only making a single copy of the data.
cast is replaced by two functions depending on the output type:
dcast
produces data frames, andacast
produces matrices/arrays.multidimensional margins are now possible:
grand_row
andgrand_col
have been dropped: now the name of the margin refers to the variable that has its value set to (all).some features have been removed such as the
|
cast operator, and the ability to return multiple values from an aggregation function. I'm reasonably sure both these operations are better performed by plyr.a new cast syntax which allows you to reshape based on functions of variables (based on the same underlying syntax as plyr):
better development practices like namespaces and tests.
the function
melt
now names the columns of its returned data frameVar1
,Var2
, ...,VarN
instead ofX1
,X2
, ...,XN
.the argument
variable.name
ofmelt
replaces the old argumentvariable_name
.
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).