melt_: Make a 'Wide' data set 'Long'

In Kmisc: Kevin Miscellaneous

Description

Inspired by reshape2:::melt, we melt data.frames and matrixs. This function is built for speed.

Usage

melt_(data, ...)

## S3 method for class 'data.frame'
melt_(data, id.vars, measure.vars,
  variable.name = "variable", ..., value.name = "value")

## S3 method for class 'matrix'
melt_(data, ...)

Arguments

data	The data.frame to melt.
...	Arguments passed to other methods.
id.vars	Vector of id variables. Can be integer (variable position) or string (variable name). If blank, we use all variables not in measure.vars.
measure.vars	Vector of measured variables. Can be integer (variable position) or string (variable name). If blank, we use all variables not in id.vars.
variable.name	Name of variable used to store measured variable names.
value.name	Name of variable used to store values.

Details

If items to be stacked are not of the same internal type, they will be promoted in the order logical > integer > numeric > character.

Examples

n <- 20
tmp <- data.frame( stringsAsFactors=FALSE,
  x=sample(letters, n, TRUE),
  y=sample(LETTERS, n, TRUE),
  za=rnorm(n),
  zb=rnorm(n),
  zc=rnorm(n)
)

stopifnot(
  identical(
    melt_(tmp, id.vars=c('x', 'y')),
    melt_(tmp, measure.vars=c('za', 'zb', 'zc'))
  )
)

Kmisc documentation built on May 29, 2017, 1:43 p.m.