#' Recode values
#'
#' This is a vectorised version of \code{\link{switch}()}: you can replace
#' numeric values based on their position, and character values by their
#' name. This is an S3 generic: dplyr provides methods for numeric, character,
#' and factors. For logical vectors, use \code{\link{if_else}}
#'
#' @param .x A vector to modify
#' @param ... Replacments. These should be named for character and factor
#' \code{.x}, and can be named for numeric \code{.x}.
#'
#' All replacements must be the same type, and must have either
#' length one or the same length as x.
#' @param .default If supplied, all values not otherwise matched will
#' be given this value. If not supplied and if the replacements are
#' the same type as the original values in \code{.x}, unmatched
#' values are not changed. If not supplied and if the replacements
#' are not compatible, unmatched values are replaced with \code{NA}.
#' \code{.default} must be either length 1 or the same length as
#' \code{.x}.
#' @param .missing If supplied, any missing values in \code{.x} will be
#' replaced by this value. Must be either length 1 or the same length as
#' \code{.x}.
#' @param .ordered If \code{TRUE}, \code{recode_factor()} creates an
#' ordered factor.
#' @return A vector the same length as \code{.x}, and the same type as
#' the first of \code{...}, \code{.default}, or \code{.missing}.
#' \code{recode_factor()} returns a factor whose levels are in the
#' same order as in \code{...}.
#' @export
#' @examples
#' # Recode values with named arguments
#' x <- sample(c("a", "b", "c"), 10, replace = TRUE)
#' recode(x, a = "Apple")
#' recode(x, a = "Apple", .default = NA_character_)
#'
#' # Named arguments also work with numeric values
#' x <- c(1:5, NA)
#' recode(x, `2` = 20L, `4` = 40L)
#'
#' # Note that if the replacements are not compatible with .x,
#' # unmatched values are replaced by NA and a warning is issued.
#' recode(x, `2` = "b", `4` = "d")
#'
#' # If you don't name the arguments, recode() matches by position
#' recode(x, "a", "b", "c")
#' recode(x, "a", "b", "c", .default = "other")
#' recode(x, "a", "b", "c", .default = "other", .missing = "missing")
#'
#' # Supply default with levels() for factors
#' x <- factor(c("a", "b", "c"))
#' recode(x, a = "Apple", .default = levels(x))
#'
#' # Use recode_factor() to create factors with levels ordered as they
#' # appear in the recode call. The levels in .default and .missing
#' # come last.
#' x <- c(1:4, NA)
#' recode_factor(x, `1` = "z", `2` = "y", `3` = "x")
#' recode_factor(x, `1` = "z", `2` = "y", .default = "D")
#' recode_factor(x, `1` = "z", `2` = "y", .default = "D", .missing = "M")
#'
#' # When the input vector is a compatible vector (character vector or
#' # factor), it is reused as default.
#' recode_factor(letters[1:3], b = "z", c = "y")
#' recode_factor(factor(letters[1:3]), b = "z", c = "y")
recode <- function(.x, ..., .default = NULL, .missing = NULL) {
UseMethod("recode")
}
#' @export
recode.numeric <- function(.x, ..., .default = NULL, .missing = NULL) {
values <- list(...)
nms <- has_names(values)
if (all(nms)) {
vals <- as.double(names(values))
} else if (all(!nms)) {
vals <- seq_along(values)
} else {
stop("Either all values must be named, or none must be named.",
call. = FALSE)
}
n <- length(.x)
template <- find_template(..., .default, .missing)
out <- template[rep(NA_integer_, n)]
replaced <- rep(FALSE, n)
for (i in seq_along(values)) {
out <- replace_with(out, .x == vals[i], values[[i]], paste0("Vector ", i))
replaced[.x == vals[i]] <- TRUE
}
.default <- validate_recode_default(.default, .x, out, replaced)
out <- replace_with(out, !replaced & !is.na(.x), .default, "`.default`")
out <- replace_with(out, is.na(.x), .missing, "`.missing`")
out
}
#' @export
recode.character <- function(.x, ..., .default = NULL, .missing = NULL) {
values <- list(...)
if (!all(has_names(values))) {
stop("All replacements must be named", call. = FALSE)
}
n <- length(.x)
template <- find_template(..., .default, .missing)
out <- template[rep(NA_integer_, n)]
replaced <- rep(FALSE, n)
for (nm in names(values)) {
out <- replace_with(out, .x == nm, values[[nm]], paste0("`", nm, "`"))
replaced[.x == nm] <- TRUE
}
.default <- validate_recode_default(.default, .x, out, replaced)
out <- replace_with(out, !replaced & !is.na(.x), .default, "`.default`")
out <- replace_with(out, is.na(.x), .missing, "`.missing`")
out
}
#' @export
recode.factor <- function(.x, ..., .default = NULL, .missing = NULL) {
values <- list(...)
if (length(values) == 0) {
stop("No replacements provided", call. = FALSE)
}
if (!all(has_names(values))) {
stop("All replacements must be named", call. = FALSE)
}
if (!is.null(.missing)) {
stop("`missing` is not supported for factors", call. = FALSE)
}
out <- rep(NA_character_, length(levels(.x)))
replaced <- rep(FALSE, length(levels(.x)))
for (nm in names(values)) {
out <- replace_with(out, levels(.x) == nm, values[[nm]], paste0("`", nm, "`"))
replaced[levels(.x) == nm] <- TRUE
}
.default <- validate_recode_default(.default, .x, out, replaced)
out <- replace_with(out, !replaced, .default, "`.default`")
levels(.x) <- out
.x
}
find_template <- function(...) {
x <- compact(list(...))
if (length(x) == 0) {
stop("No replacements provided", call. = FALSE)
}
x[[1]]
}
validate_recode_default <- function(default, x, out, replaced) {
default <- recode_default(x, default, out)
if (is.null(default) && sum(replaced & !is.na(x)) < length(out[!is.na(x)])) {
warning("Unreplaced values treated as NA as .x is not compatible. ",
"Please specify replacements exhaustively or supply .default",
call. = FALSE)
}
default
}
recode_default <- function(x, default, out) {
UseMethod("recode_default")
}
recode_default.default <- function(x, default, out) {
same_type <- identical(typeof(x), typeof(out))
if (is.null(default) && same_type) {
x
} else {
default
}
}
recode_default.factor <- function(x, default, out) {
if (is.null(default) && is.factor(x)) {
levels(x)
} else {
default
}
}
#' @rdname recode
#' @export
recode_factor <- function (.x, ..., .default = NULL, .missing = NULL,
.ordered = FALSE) {
recoded <- recode(.x, ..., .default = .default, .missing = .missing)
all_levels <- unique(c(..., recode_default(.x, .default, recoded), .missing))
recoded_levels <- if (is.factor(recoded)) levels(recoded) else unique(recoded)
levels <- intersect(all_levels, recoded_levels)
factor(recoded, levels, ordered = .ordered)
}
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