R/round2.R

In mrdwab/mrdwabmisc: Miscellaneous R functions, mostly for data processing

#' Round Numbers the Way You Learned in School
#' 
#' The \code{\link{round2}} function rounds numbers in the way you probably
#' learned in school, that is, round up to the next number for values of 5 and
#' above.
#' 
#' To reduce bias in rounding, R's \code{\link{round}} function uses a
#' "round-to-even" approach. Still, many people are surprised when they find
#' that R's \code{round} function will return the same value for
#' \code{round(1.5)} and \code{round(2.5)}. This function uses the rounding
#' approach found in most school lessons and in software like Excel to make the
#' results comparable.
#' 
#' @param x The number (or vector of numbers) that needs rounding.
#' @param digits The number of decimal places in the output.
#' @author Unknown (see "References")
#' @seealso \code{\link{round}}
#' @references Function originally found in an anonymous comment at the
#' Statistically Significant blog. See
#' \url{http://www.webcitation.org/68djeLBtJ}
#' @examples
#' 
#' input <- seq(from = 0.5, by = 1, length.out = 10)
#' round(input)
#' round2(input)
#' round(input/10, digits = 1)
#' round2(input/10, digits = 1)
#' \dontshow{rm(input)}
#' 
#' @export round2
round2 <- function(x, digits = 0) {
  z <- (abs(x) * 10 ^ digits) + 0.5
  (trunc(z)/10^digits) * sign(x)
}