alply {plyr}R Documentation

Split array, apply function, and return results in a list.

Description

For each slice of an array, apply function then combine results into a list. alply is somewhat similar to apply for cases where the results are not atomic.

Usage

  alply(.data, .margins, .fun = NULL, ..., .expand = TRUE,
    .progress = "none", .parallel = FALSE)

Arguments

.fun

function to apply to each piece

...

other arguments passed on to .fun

.progress

name of the progress bar to use, see create_progress_bar

.data

matrix, array or data frame to be processed

.margins

a vector giving the subscripts to split up data by. 1 splits up by rows, 2 by columns and c(1,2) by rows and columns, and so on for higher dimensions

.expand

if .data is a data frame, should output be 1d (expand = FALSE), with an element for each row; or nd (expand = TRUE), with a

.parallel

if TRUE, apply function in parallel, using parallel backend provided by foreach dimension for each variable.

Value

list of results

Input

This function splits matrices, arrays and data frames by dimensions

Output

If there are no results, then this function will return a list of length 0 (list()).

References

Hadley Wickham (2011). The Split-Apply-Combine Strategy for Data Analysis. Journal of Statistical Software, 40(1), 1-29. http://www.jstatsoft.org/v40/i01/.

See Also

Other array input: aaply, adply

Other list output: dlply, llply

Examples

alply(ozone, 3, quantile)
alply(ozone, 3, function(x) table(round(x)))

[Package plyr version 1.7.1 Index]