``` f3126e0b » hadley ``` 2008-09-15 Basic combinatorial documentation for plyr functions 1 Split list, apply function, and return results in a data frame 2 For each element of a list, apply function then combine results into a data frame 3 ``` 6b4111e8 » hadley ``` 2008-10-07 Use . as prefix, not suffix 4 All plyr functions use the same split-apply-combine strategy: they split the input into simpler pieces, apply \code{.fun} to each piece, and then combine the pieces into a single data structure. This function splits ``` f3126e0b » hadley ``` 2008-09-15 Basic combinatorial documentation for plyr functions 5 6 matrices, arrays and data frames by dimensions 7 data frames by variable 8 lists by elements 9 10 and combines the result into a data frame 11 and combines the result into an array 12 and combines the result into a list 13 and discards the output 14 15 If there are no results, then this function will return 16 17 a data frame with zero rows and columns (\code{data.frame()}). 18 a vector of length 0 (\code{vector()}). 19 a list of length 0 (\code{list()}). 20 21 See \code{vignette("intro", "plyr")} for more details, description and case studies. 22 23 @keyword manip 24 25 @arguments matrix, array or data frame to be processed 26 @arguments list to be processed 27 @arguments data frame to be processed 28 29 @arguments variables to split data frame by, as quoted variables, a formula or character vector 30 @arguments a vector giving the subscripts to split up \code{data} by. 1 splits up by rows, 2 by columns and c(1,2) by rows and columns, and so on for higher dimensions 31 32 @arguments function to apply to each piece ``` 6b4111e8 » hadley ``` 2008-10-07 Use . as prefix, not suffix 33 @arguments other arguments passed on to \code{.fun} ``` f3126e0b » hadley ``` 2008-09-15 Basic combinatorial documentation for plyr functions 34 @arguments name of the progress bar to use, see \code{\link{create_progress_bar}} 35 ``` 4dec3876 » hadley ``` 2008-09-15 Complete documentation 36 @value if results are atomic with same type and dimensionality, a vector, matrix or array; otherwise, a list-array (a list with dimensions) ``` f3126e0b » hadley ``` 2008-09-15 Basic combinatorial documentation for plyr functions 37 @value list of results 38 @value a data frame