By Alex

2012-09-11 20:22:00 8 Comments

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?


@Matt Parker 2012-09-11 22:50:34

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

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.

@isomorphismes 2014-09-07 21:10:29

Thanks Matt! Appreciate you posting this from the mail list to the more publicly familiar forum here.

@landroni 2015-10-15 16:45:49

the ability to return multiple values from an aggregation function See related question:…

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