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#' Shuffle Variables
#'
#' `step_shuffle` creates a *specification* of a recipe
#' step that will randomly change the order of rows for selected
#' variables.
#'
#' @inheritParams step_center
#' @param columns A character string that contains the names of
#' columns that should be shuffled. These values are not determined
#' until [prep()] is called.
#' @template step-return
#' @details
#'
#' # Tidying
#'
#' When you [`tidy()`][tidy.recipe()] this step, a tibble with column
#' `terms` (the columns that will be permuted) is returned.
#'
#' @template case-weights-not-supported
#'
#' @family row operation steps
#' @export
#' @examples
#' integers <- data.frame(A = 1:12, B = 13:24, C = 25:36)
#'
#' library(dplyr)
#' rec <- recipe(~ A + B + C, data = integers) %>%
#' step_shuffle(A, B)
#'
#' rand_set <- prep(rec, training = integers)
#'
#' set.seed(5377)
#' bake(rand_set, integers)
#'
#' tidy(rec, number = 1)
#' tidy(rand_set, number = 1)
step_shuffle <- function(recipe,
...,
role = NA,
trained = FALSE,
columns = NULL,
skip = FALSE,
id = rand_id("shuffle")) {
add_step(
recipe,
step_shuffle_new(
terms = enquos(...),
role = role,
trained = trained,
columns = columns,
skip = skip,
id = id
)
)
}
step_shuffle_new <- function(terms, role, trained, columns, skip, id) {
step(
subclass = "shuffle",
terms = terms,
role = role,
trained = trained,
columns = columns,
skip = skip,
id = id
)
}
#' @export
prep.step_shuffle <- function(x, training, info = NULL, ...) {
col_names <- recipes_eval_select(x$terms, training, info)
step_shuffle_new(
terms = x$terms,
role = x$role,
trained = TRUE,
columns = col_names,
skip = x$skip,
id = x$id
)
}
#' @export
bake.step_shuffle <- function(object, new_data, ...) {
check_new_data(names(object$columns), object, new_data)
if (nrow(new_data) == 1) {
rlang::warn("`new_data` contains a single row; unable to shuffle")
return(new_data)
}
if (length(object$columns) > 0) {
for (i in seq_along(object$columns)) {
new_data[, object$columns[i]] <-
sample(getElement(new_data, object$columns[i]))
}
}
new_data
}
print.step_shuffle <-
function(x, width = max(20, options()$width - 22), ...) {
title <- "Shuffled "
print_step(x$columns, x$terms, x$trained, title, width)
invisible(x)
}
#' @rdname tidy.recipe
#' @export
tidy.step_shuffle <- function(x, ...) {
res <- simple_terms(x, ...)
res$id <- x$id
res
}
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