plyr: alply – R documentation

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plyr

alply

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

Examples

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

plyr

Tools for Splitting, Applying and Combining Data

v1.8.6

MIT + file LICENSE

Authors

Hadley Wickham [aut, cre]

Initial release

alply

Description

Usage

Arguments

Details

Value

Input

Output

References

See Also

Examples

plyr

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