reshape2: Flexibly Reshape Data: A Reboot of the Reshape Package.

データ整形ツール（Rでピボットテーブルのような操作）

> library(reshape2)


Attaching package: 'reshape2'

The following objects are masked from 'package:reshape':

    colsplit, melt, recast

> data("tips")

バージョン: 1.4.1

関数名	概略
`add_margins`	Add margins to a data frame.
`cast`	Cast functions Cast a molten data frame into an array or data frame.
`colsplit`	Split a vector into multiple columns
`french_fries`	Sensory data from a french fries experiment.
`melt`	Convert an object into a molten data frame.
`melt.array`	Melt an array.
`melt.data.frame`	Melt a data frame into form suitable for easy casting.
`melt.default`	Melt a vector. For vectors, makes a column of a data frame
`melt.list`	Melt a list by recursively melting each component.
`melt_check`	Check that input variables to melt are appropriate.
`parse_formula`	Parse casting formulae.
`recast`	Recast: melt and cast in a single step
`smiths`	Demo data describing the Smiths.
`tips`	Tipping data

add_margins

cast / dcast / acast

Arguments

data
formula
...
margins
subset
fill
drop
value.var

melt

データフレーム、配列や行列、リストに対応

Arguments

data
...
- id.vars
- measure.vars
- factorsAsStrings
na.rm
value.name

> melt(data          = airquality, 
+      id.vars       = c("Month", "Day"),
+      variable.name = "Factor", # 新たな列の名前
+      value.name    = "Value") %>% # 新たな列の名前
+   head()

  Month Day variable value
1     5   1    Ozone    41
2     5   2    Ozone    36
3     5   3    Ozone    12
4     5   4    Ozone    18
5     5   5    Ozone    NA
6     5   6    Ozone    28

tips

> tips %>% {
+   print(class(.))
+   dplyr::tbl_df(.)
+ }

[1] "data.frame"

# A tibble: 244 x 7
   total_bill   tip    sex smoker    day   time  size
*       <dbl> <dbl> <fctr> <fctr> <fctr> <fctr> <int>
1       16.99  1.01 Female     No    Sun Dinner     2
2       10.34  1.66   Male     No    Sun Dinner     3
3       21.01  3.50   Male     No    Sun Dinner     3
4       23.68  3.31   Male     No    Sun Dinner     2
5       24.59  3.61 Female     No    Sun Dinner     4
6       25.29  4.71   Male     No    Sun Dinner     4
7        8.77  2.00   Male     No    Sun Dinner     2
8       26.88  3.12   Male     No    Sun Dinner     4
9       15.04  1.96   Male     No    Sun Dinner     2
10      14.78  3.23   Male     No    Sun Dinner     2
# ... with 234 more rows