Created a preprocessing step that limits the size of the training window

NAMESPACE

@@ -5,9 +5,11 @@ S3method(Ops,dist_quantiles)
 S3method(apply_frosting,default)
 S3method(apply_frosting,epi_workflow)
 S3method(augment,epi_workflow)
+S3method(bake,epi_recipe)
 S3method(bake,step_epi_ahead)
 S3method(bake,step_epi_lag)
 S3method(bake,step_population_scaling)
+S3method(bake,step_training_window)
 S3method(detect_layer,frosting)
 S3method(detect_layer,workflow)
 S3method(epi_keys,default)
@@ -36,10 +38,12 @@ S3method(prep,epi_recipe)
 S3method(prep,step_epi_ahead)
 S3method(prep,step_epi_lag)
 S3method(prep,step_population_scaling)
+S3method(prep,step_training_window)
 S3method(print,epi_workflow)
 S3method(print,frosting)
 S3method(print,step_epi_ahead)
 S3method(print,step_epi_lag)
+S3method(print,step_training_window)
 S3method(quantile,dist_quantiles)
 S3method(refresh_blueprint,default_epi_recipe_blueprint)
 S3method(residuals,flatline)
@@ -105,6 +109,7 @@ export(step_epi_ahead)
 export(step_epi_lag)
 export(step_epi_naomit)
 export(step_population_scaling)
+export(step_training_window)
 export(validate_layer)
 import(distributional)
 import(recipes)
@@ -119,7 +124,9 @@ importFrom(rlang,":=")
 importFrom(rlang,`%||%`)
 importFrom(rlang,abort)
 importFrom(rlang,caller_env)
+importFrom(rlang,is_empty)
 importFrom(rlang,is_null)
+importFrom(rlang,quos)
 importFrom(stats,as.formula)
 importFrom(stats,family)
 importFrom(stats,lm)
@@ -130,4 +137,6 @@ importFrom(stats,predict)
 importFrom(stats,qnorm)
 importFrom(stats,quantile)
 importFrom(stats,residuals)
+importFrom(stats,setNames)
+importFrom(tibble,is_tibble)
 importFrom(tibble,tibble)

R/bake.epi_recipe.R

@@ -0,0 +1,104 @@
+#' Bake an epi_recipe
+#'
+#' @param object A trained object such as a [recipe()] with at least
+#'   one preprocessing operation.
+#' @param new_data An `epi_df`, data frame or tibble for whom the
+#'   preprocessing will be applied. If `NULL` is given to `new_data`,
+#'   the pre-processed _training data_ will be returned.
+#' @param ... One or more selector functions to choose which variables will be
+#'   returned by the function. See \code{\link[selections]{recipes}} for
+#'   more details. If no selectors are given, the default is to
+#'   use [everything()].
+#' @return An `epi_df` that may have different columns than the
+#' original columns in `new_data`.
+#' @importFrom rlang is_empty quos
+#' @importFrom tibble is_tibble
+#' @rdname bake
+#' @export
+bake.epi_recipe <- function(object, new_data, ...) {
+
+  if (rlang::is_missing(new_data)) {
+    rlang::abort("'new_data' must be either an epi_df or NULL. No value is not allowed.")
+  }
+
+  if (is.null(new_data)) {
+    return(epi_juice(object, ...))
+  }
+
+  if (!fully_trained(object)) {
+    rlang::abort("At least one step has not been trained. Please run `prep`.")
+  }
+
+  terms <- quos(...)
+  if (is_empty(terms)) {
+    terms <- quos(everything())
+  }
+
+  # In case someone used the deprecated `newdata`:
+  if (is.null(new_data) || is.null(ncol(new_data))) {
+    if (any(names(terms) == "newdata")) {
+      rlang::abort("Please use `new_data` instead of `newdata` with `bake`.")
+    } else {
+      rlang::abort("Please pass a data set to `new_data`.")
+    }
+  }
+
+  if (!is_tibble(new_data)) {
+    new_data <- as_tibble(new_data)
+  }
+
+  recipes:::check_role_requirements(object, new_data)
+
+  recipes:::check_nominal_type(new_data, object$orig_lvls)
+
+  # Drop completely new columns from `new_data` and reorder columns that do
+  # still exist to match the ordering used when training
+  original_names <- names(new_data)
+  original_training_names <- unique(object$var_info$variable)
+  bakeable_names <- intersect(original_training_names, original_names)
+  new_data <- new_data[, bakeable_names]
+
+  n_steps <- length(object$steps)
+
+  for (i in seq_len(n_steps)) {
+    step <- object$steps[[i]]
+
+    if (recipes:::is_skipable(step)) {
+      next
+    }
+
+    new_data <- bake(step, new_data = new_data)
+
+    if (!is_tibble(new_data)) {
+      abort("bake() methods should always return tibbles")
+    }
+  }
+
+  # Use `last_term_info`, which maintains info on all columns that got added
+  # and removed from the training data. This is important for skipped steps
+  # which might have resulted in columns not being added/removed in the test
+  # set.
+  info <- object$last_term_info
+
+  # Now reduce to only user selected columns
+  out_names <- recipes_eval_select(terms, new_data, info,
+                                   check_case_weights = FALSE)
+  new_data <- new_data[, out_names]
+
+  # The levels are not null when no nominal data are present or
+  # if strings_as_factors = FALSE in `prep`
+  if (!is.null(object$levels)) {
+    var_levels <- object$levels
+    var_levels <- var_levels[out_names]
+    check_values <-
+      vapply(var_levels, function(x) {
+        (!all(is.na(x)))
+      }, c(all = TRUE))
+    var_levels <- var_levels[check_values]
+    if (length(var_levels) > 0) {
+      new_data <- recipes:::strings2factors(new_data, var_levels)
+    }
+  }
+
+  new_data
+}

R/epi_juice.R

@@ -0,0 +1,42 @@
+#' Extract transformed training set
+#'
+#' @inheritParams bake.epi_recipe
+epi_juice <- function(object, ...) {
+  if (!fully_trained(object)) {
+    rlang::abort("At least one step has not been trained. Please run `prep()`.")
+  }
+
+  if (!isTRUE(object$retained)) {
+    rlang::abort(paste0(
+      "Use `retain = TRUE` in `prep()` to be able ",
+      "to extract the training set"
+    ))
+  }
+
+  terms <- quos(...)
+  if (is_empty(terms)) {
+    terms <- quos(everything())
+  }
+
+  # Get user requested columns
+  new_data <- object$template
+  out_names <- recipes_eval_select(terms, new_data, object$term_info,
+                                   check_case_weights = FALSE)
+  new_data <- new_data[, out_names]
+
+  # Since most models require factors, do the conversion from character
+  if (!is.null(object$levels)) {
+    var_levels <- object$levels
+    var_levels <- var_levels[out_names]
+    check_values <-
+      vapply(var_levels, function(x) {
+        (!all(is.na(x)))
+      }, c(all = TRUE))
+    var_levels <- var_levels[check_values]
+    if (length(var_levels) > 0) {
+      new_data <- recipes:::strings2factors(new_data, var_levels)
+    }
+  }
+
+  new_data
+}

R/training_window.R

@@ -0,0 +1,104 @@
+#' Limits the size of the training window to the most recent observations
+#'
+#' `step_training_window` creates a *specification* of a recipe step that
+#'   limit the size of the training window to the `n_recent` most recent
+#'   observations in `time_value` per group, where the groups are formed
+#'   based on the remaining `epi_keys`.
+#'
+#' @param recipe A recipe object. The step will be added to the
+#'  sequence of operations for this recipe.
+#' @param role Not used by this step since no new variables are created.
+#' @param trained A logical to indicate if the quantities for
+#'  preprocessing have been estimated.
+#' @param n_recent An integer value that represents the number of most recent
+#' observations that are to be kept in the training window per location.
+#' The default value is 50.
+#' @param id A character string that is unique to this step to identify it.
+#' @template step-return
+#'
+#' @details Note that `step_epi_lead()` and `step_epi_lag()` should come
+#' after any filtering step.
+#'
+#' @export
+#'
+#' @examples
+#' tib <- tibble::tibble(
+#' x = 1:10, y = 1:10,
+#' time_value = rep(seq(as.Date("2020-01-01"), by = 1,
+#'                      length.out = 5), times = 2),
+#' geo_value = rep(c("ca", "hi"), each = 5)
+#' ) %>% epiprocess::as_epi_df()
+#'
+#' library(recipes)
+#' epi_recipe(y ~ x, data = tib) %>%
+#'   step_training_window(n_recent = 3) %>%
+#'   prep(tib) %>%
+#'   bake(new_data = NULL)
+step_training_window <-
+  function(recipe,
+           role = NA,
+           trained = FALSE,
+           n_recent = 50,
+           id = rand_id("training_window")) {
+
+    add_step(
+      recipe,
+      step_training_window_new(
+        role = role,
+        trained = trained,
+        n_recent = n_recent,
+        skip = TRUE,
+        id = id
+      )
+    )
+  }
+
+step_training_window_new <-
+  function(terms, role, trained, n_recent, skip, id = id) {
+    step(
+      subclass = "training_window",
+      role = role,
+      trained = trained,
+      n_recent = n_recent,
+      skip = skip,
+      id = id
+    )
+  }
+
+#' @export
+prep.step_training_window <- function(x, training, info = NULL) {
+
+  step_training_window_new(
+    role = x$role,
+    trained = TRUE,
+    n_recent = x$n_recent,
+    skip = x$skip,
+    id = x$id
+  )
+}
+
+#' @export
+bake.step_training_window <- function(object, new_data) {
+  if (!all(object$n_recent == as.integer(object$n_recent))) {
+    rlang::abort("step_training_window requires 'n_recent' to be integer valued.")
+  }
+
+  ek <- epi_keys(new_data)[which(epi_keys(new_data) != "time_value")]
+
+  new_data %>%
+    dplyr::group_by(dplyr::across(dplyr::all_of(ek))) %>%
+    dplyr::arrange(time_value) %>%
+    dplyr::slice_tail(n = object$n_recent) %>%
+    dplyr::ungroup()
+}
+
+#' @export
+print.step_training_window <-
+  function(x, width = max(20, options()$width - 30), ...) {
+    title <- "Number of most recent observations per location used in training window "
+    n_recent = x$n_recent
+    tr_obj = format_selectors(rlang::enquos(n_recent), width)
+    recipes::print_step(tr_obj, rlang::enquos(n_recent),
+                        x$trained, title, width)
+    invisible(x)
+  }