#' @title Group the rows of a data frame into a given number groups
#' @export
#' @family Grouped data frame targets
#' @description Create a target that outputs a grouped data frame
#' for downstream dynamic branching. Set the maximum
#' number of groups using `count`. The number of rows per group
#' varies but is approximately uniform.
#' @return A target object to generate a grouped data frame
#' to allows downstream dynamic targets to branch over the
#' groups of rows.
#' See the "Target objects" section for background.
#' @inheritSection tar_map Target objects
#' @inheritParams targets::tar_target
#' @param count Positive integer, maximum number of row groups
#' @examples
#' if (identical(Sys.getenv("TAR_LONG_EXAMPLES"), "true")) {
#' targets::tar_dir({ # tar_dir() runs code from a temporary directory.
#' targets::tar_script({
#' produce_data <- function() {
#' expand.grid(var1 = c("a", "b"), var2 = c("c", "d"), rep = c(1, 2, 3))
#' }
#' list(
#' tarchetypes::tar_group_count(data, produce_data(), count = 2),
#' tar_target(group, data, pattern = map(data))
#' )
#' })
#' targets::tar_make()
#' # Read the first row group:
#' targets::tar_read(group, branches = 1)
#' # Read the second row group:
#' targets::tar_read(group, branches = 2)
#' })
#' }
tar_group_count <- function(
name,
command,
count,
tidy_eval = targets::tar_option_get("tidy_eval"),
packages = targets::tar_option_get("packages"),
library = targets::tar_option_get("library"),
format = targets::tar_option_get("format"),
repository = targets::tar_option_get("repository"),
error = targets::tar_option_get("error"),
memory = targets::tar_option_get("memory"),
garbage_collection = targets::tar_option_get("garbage_collection"),
deployment = targets::tar_option_get("deployment"),
priority = targets::tar_option_get("priority"),
resources = targets::tar_option_get("resources"),
storage = targets::tar_option_get("storage"),
retrieval = targets::tar_option_get("retrieval"),
cue = targets::tar_option_get("cue"),
description = targets::tar_option_get("description")
) {
targets::tar_assert_package("dplyr")
name <- targets::tar_deparse_language(substitute(name))
targets::tar_assert_lgl(tidy_eval, "tidy_eval must be logical.")
count <- as.integer(count)
targets::tar_assert_nonempty(count, "count must be nonempty.")
targets::tar_assert_scalar(count, "count must have length 1.")
targets::tar_assert_dbl(count, "count must be numeric.")
targets::tar_assert_ge(count, 1L, "count must be at least 1.")
command <- substitute(command)
command <- tar_group_count_command(command, count, tidy_eval)
targets::tar_target_raw(
name = name,
command = command,
packages = packages,
library = library,
format = format,
repository = repository,
iteration = "group",
error = error,
memory = memory,
garbage_collection = garbage_collection,
deployment = deployment,
priority = priority,
resources = resources,
storage = storage,
retrieval = retrieval,
cue = cue,
description = description
)
}
tar_group_count_command <- function(command, count, tidy_eval) {
envir <- targets::tar_option_get("envir")
targets::tar_assert_envir(envir)
command <- targets::tar_tidy_eval(command, envir, tidy_eval)
fun <- call_ns("tarchetypes", "tar_group_count_run")
as.call(list(fun, data = command, count))
}
#' @title Generate a grouped data frame within `tar_group_count()`.
#' @export
#' @keywords internal
#' @description Not a user-side function. Do not invoke directly.
#' @inheritParams tar_group_count_index
tar_group_count_run <- function(data, count) {
data$tar_group <- tar_group_count_index(data = data, count = count)
data
}
#' @title Generate the tar_group column for `tar_group_count()`.
#' @export
#' @keywords internal
#' @description Not a user-side function. Do not invoke directly.
#' @param data A data frame to group.
#' @param count Maximum number of groups.
tar_group_count_index <- function(data, count) {
targets::tar_assert_df(data, "tar_group_count() output must be a data frame.")
count <- min(count, nrow(data))
if_any(
count > 1L,
as.integer(cut(seq_len(nrow(data)), breaks = count)),
rep(1L, nrow(data))
)
}
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