reshape vs. reshape2 in R

50
votes

I am attempting to understand why development had shifted from reshape to reshape2 package. They seem to be functionally the same, however, I am unable to upgrade to reshape2 currently due to an older version of R running on the server. I am concerned about the possibility of a major bug that would have shifted development to a whole new package instead of simply continuing development of reshape. Does anyone know if there is a major flaw in the reshape package?

1
rreshapereshape2
reshape2 replaced reshape. But what is your question? – Andrie
You found the official docs right? cran.r-project.org/web/packages/reshape2/reshape2.pdf How about this explanation of how to use reshape2? wiki.stdout.org/rcookbook/Manipulating%20data/… – Wilduck
Reshape was on old version of a package. From what I've observed Hadley Wickham is pretty concerned with breaking the code of people relying on his packages. I'm guessing reshape needed some major overhauls, rather than breaking everyone's code eh started over from scratch (I'm guessing). There's a few differences in functions and usage but they do very similar kobs. I'd recommend you stick with reshape2 as I don't believe reshape is being developed anymore. – Tyler Rinker
@Maiasaura, I can't upgrade to reshape2 because my sys admin runs an old version of R. Therefore, I needed to know if there was some major bug that caused Hadley to build reshape2. – Alex
So it sounds like your real (and answerable) question is: "Did Hadley Wickham shift his efforts to reshape2 because of a major bug in reshape?" – Josh O'Brien

1 Answers

68
votes

reshape2 let Hadley make a rebooted reshape that was way, way faster, while avoiding busting up people's dependencies and habits.

https://stat.ethz.ch/pipermail/r-packages/2010/001169.html

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:

  • 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, and acast produces matrices/arrays.

  • multidimensional margins are now possible: grand_row and grand_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.