plyr (version 1.1)

splitter_d: Split a data frame by variables.

Description

Split a data frame by variables. Split a data frame into pieces based on variable contained in that data frame

Usage

splitter_d(data, .variables, drop=TRUE)

Arguments

data

data frame

.variables

a quoted list of variables, a formula, or character vector. NULL will not split the data

drop

drop unnused factor levels?

Value

• a list of data.frames, with attributes that record split details

Details

This is the workhorse of the d*ply functions. Based on the variables you supply, it breaks up a single data frame into a list of data frames, each containing a single combination from the levels of the specified variables.

This is basically a thin wrapper around split which evaluates the variables in the context of the data, and includes enough information to reconstruct the labelling of the data frame after other operations.

See Also

. for quoting variables, split

Examples

plyr:::splitter_d(mtcars, .(cyl))
plyr:::splitter_d(mtcars, .(vs, am))
plyr:::splitter_d(mtcars, .(am, vs))

mtcars$cyl2 <- factor(mtcars$cyl, levels = c(2, 4, 6, 8, 10))
plyr:::splitter_d(mtcars, .(cyl2), drop = TRUE)
plyr:::splitter_d(mtcars, .(cyl2), drop = FALSE)

mtcars$cyl3 <- ifelse(mtcars$vs == 1, NA, mtcars$cyl)
plyr:::splitter_d(mtcars, .(cyl3))
plyr:::splitter_d(mtcars, .(cyl3, vs))
plyr:::splitter_d(mtcars, .(cyl3, vs), drop = FALSE)