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

In plyr: Tools for Splitting, Applying and Combining Data

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.

Usage

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

Arguments

.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
.fun	function to apply to each piece
...	other arguments passed on to .fun
.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.
.progress	name of the progress bar to use, see create_progress_bar
.inform	produce informative error messages? This is turned off by default because it substantially slows processing speed, but is very useful for debugging
.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.
.dims	if TRUE, copy over dimensions and names from input.

Details

The list will have "dims" and "dimnames" corresponding to the margins given. For instance alply(x, c(3,2), ...) where x has dims c(4,3,2) will give a result with dims c(2,3).

alply is somewhat similar to apply for cases where the results are not atomic.

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. https://www.jstatsoft.org/v40/i01/.

See Also

Other array input: a_ply(), aaply(), adply()

Other list output: dlply(), llply(), mlply()

Examples

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

plyr documentation built on Oct. 2, 2023, 9:07 a.m.