plyr (version 1.5.2)

ldply: Split list, apply function, and return results in a data frame.

Description

Split list, apply function, and return results in a data frame. For each element of a list, apply function then combine results into a data frame

Usage

ldply(.data, .fun, ..., .progress="none", .parallel=FALSE)

Arguments

.data

list to be processed

.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

Value

• a data frame

Details

All plyr functions use the same split-apply-combine strategy: they split the input into simpler pieces, apply .fun to each piece, and then combine the pieces into a single data structure. This function splits lists by elements and combines the result into a data frame. If there are no results, then this function will return a data frame with zero rows and columns (data.frame()).

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.

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/.