1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
|
# reshape2
<!-- badges: start -->
[](https://github.com/hadley/reshape/actions)
[](https://codecov.io/gh/hadley/reshape?branch=master)
<!-- badges: end -->
## Status
[](https://img.shields.io/badge/lifecycle-retired-orange.svg)
reshape2 is retired: only changes necessary to keep it on CRAN will be made. We recommend using [tidyr](http://tidyr.tidyverse.org/) 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, 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.
* the function `melt` now names the columns of its returned data frame `Var1`, `Var2`, ..., `VarN` instead of `X1`, `X2`, ..., `XN`.
* the argument `variable.name` of `melt` replaces the old argument `variable_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).
|
