adply {plyr}R Documentation

Split array, apply function, and return results in a data frame.

Description

For each slice of an array, apply function then combine results into a data frame.

Usage

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

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

.parallel

if TRUE, apply function in parallel, using parallel backend provided by foreach

.paropts

a list of additional options passed into the foreach function when parallel computation is enabled. This is important if (for example) your code relies on external data or packages: use the .export and .packages arguments to supply them so that all cluster nodes have the correct environment set up for computing.

.inform

produce informative error messages? This is turned off by by default because it substantially slows processing speed, but is very useful for debugging

.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 dimension for each variable.

Value

A data frame, as described in the output section.

Input

This function splits matrices, arrays and data frames by dimensions

Output

The most unambiguous behaviour is achieved when .fun returns a data frame - in that case pieces will be combined with rbind.fill. If .fun returns an atomic vector of fixed length, it will be rbinded together and converted to a data frame. Any other values will result in an error.

If there are no results, then this function will return a data frame with zero rows and columns (data.frame()).

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: a_ply, aaply, alply

Other data frame output: ddply, ldply, mdply


[Package plyr version 1.8 Index]