R/fsapply.R

In rje: Miscellaneous Useful Functions for Statistics

#' Fast and loose application of function over list.
#' 
#' Faster highly stripped down version of \code{sapply()}
#' 
#' This is just a wrapper for \code{unlist(lapply(x, FUN))}, which will behave
#' as \code{sapply} if \code{FUN} returns an atomic vector of length 1 each
#' time.
#' 
#' Speed up over sapply is not dramatic, but can be useful in time critical
#' code.
#' 
#' @param x a vector (atomic or list) or an expression object.
#' @param FUN the function to be applied to each element of \code{x}. In the
#' case of functions like \code{+}, the function name must be backquoted or
#' quoted.
#' @return A vector of results of applying \code{FUN} to \code{x}.
#' @section Warning : Very loose version of \code{sapply} which should really
#' only by used if you're confident about how \code{FUN} is applied to each
#' entry in \code{x}.
#' @author Robin Evans
#' @keywords list
#' @examples
#' 
#' x = list(1:1000)
#' tmp = fsapply(x, sin)
#' 
#' \dontrun{
#' x = list()
#' set.seed(142313)
#' for (i in 1:1000) x[[i]] = rnorm(100)
#' 
#' system.time(for (i in 1:100) sapply(x, function(x) last(x)))
#' system.time(for (i in 1:100) fsapply(x, function(x) last(x)))
#' }
#' 
#' @export fsapply
fsapply <-
function (x, FUN) 
unlist(lapply(x, FUN))