R/mapvalues.R

In DavidJesse21/data.table.utils: Extra Functions for the data.table Package

#' Replace values of a vector based on a mapping scheme.
#'
#' @description This is basically a copy or reimplementation of the
#'   \code{plyr::mapvalues()} function.
#'   It takes an input vector \code{x} as well as two vectors \code{from} and
#'   \code{to} that act as a dictionary for the mapping.
#'
#' @param x (`any`)\cr
#'   A vector.
#' @param from (`any`)\cr
#'   A vector specifying the values that should be mapped.
#' @param to (`any`)\cr
#'   A vector specifying the values to map to.
#'
#' @return (`any`)\cr
#'   A vector. It may be of a different type than the input vector `x`,
#'   depending on your inputs for `from` and `to`.
#'
#' @importFrom checkmate assert_atomic_vector
#'
#' @export
mapvalues = function(x, from, to) {
  assert_atomic_vector(x, min.len = 1L)
  assert_atomic_vector(from, min.len = 1L, unique = TRUE)
  assert_atomic_vector(to, min.len = 1L)

  if (!same_length(from, to)) {
    stop("Vectors `from` and `to` must have the same length.")
  }

  if (!all(unique(x) %in% from)) {
    stop("`from` must cover all unique values in `x`.")
  }


  if (is.factor(x)) {
    levels(x) = mapvalues(levels(x), from, to)
    return(x)
  }

  mapidx = match(x, from)
  return(to[mapidx])
}