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#' Add many differenced columns to the data
#'
#' A handy function for adding multiple lagged difference values to a data frame.
#' Works with `dplyr` groups too.
#'
#' @param .data A tibble.
#' @param .value One or more column(s) to have a transformation applied. Usage
#' of `tidyselect` functions (e.g. `contains()`) can be used to select multiple columns.
#' @param .lags One or more lags for the difference(s)
#' @param .differences The number of differences to apply.
#' @param .log If TRUE, applies log-differences.
#' @param .names A vector of names for the new columns. Must be of same length as the
#' number of output columns. Use "auto" to automatically rename the columns.
#'
#'
#' @return Returns a `tibble` object describing the timeseries.
#'
#' @details
#'
#' __Benefits__
#'
#' This is a scalable function that is:
#'
#' - Designed to work with grouped data using `dplyr::group_by()`
#' - Add multiple differences by adding a sequence of differences using
#' the `.lags` argument (e.g. `lags = 1:20`)
#'
#'
#' @seealso
#'
#' Augment Operations:
#'
#' - [tk_augment_timeseries_signature()] - Group-wise augmentation of timestamp features
#' - [tk_augment_holiday_signature()] - Group-wise augmentation of holiday features
#' - [tk_augment_slidify()] - Group-wise augmentation of rolling functions
#' - [tk_augment_lags()] - Group-wise augmentation of lagged data
#' - [tk_augment_differences()] - Group-wise augmentation of differenced data
#' - [tk_augment_fourier()] - Group-wise augmentation of fourier series
#'
#' Underlying Function:
#'
#' - [`diff_vec()`] - Underlying function that powers `tk_augment_differences()`
#'
#' @examples
#' library(dplyr)
#'
#' m4_monthly %>%
#' group_by(id) %>%
#' tk_augment_differences(value, .lags = 1:20)
#'
#' @name tk_augment_differences
NULL
#' @export
#' @rdname tk_augment_differences
tk_augment_differences <- function(.data,
.value,
.lags = 1,
.differences = 1,
.log = FALSE,
.names = "auto") {
# Checks
column_expr <- enquo(.value)
if (rlang::quo_is_missing(column_expr)) stop(call. = FALSE, "tk_augment_differences(.value) is missing.")
# if (rlang::is_missing(.lags)) stop(call. = FALSE, "tk_augment_differences(.lags) is missing.")
# if (rlang::is_missing(.differences)) stop(call. = FALSE, "tk_augment_differences(.differences) is missing.")
if (!any(.names == "auto")) {
if (length(.names) != length(.lags) * length(.differences)) {
rlang::abort(".names must be a vector of length ", length(.lags) * length(.differences))
}
}
UseMethod("tk_augment_differences", .data)
}
#' @export
tk_augment_differences.data.frame <- function(.data,
.value,
.lags = 1,
.differences = 1,
.log = FALSE,
.names = "auto") {
# column_expr <- enquo(.value)
col_nms <- names(tidyselect::eval_select(rlang::enquo(.value), .data))
make_call <- function(col, lag_val, diff_val) {
rlang::call2(
"diff_vec",
x = rlang::sym(col),
lag = lag_val,
difference = diff_val,
log = .log,
silent = TRUE,
.ns = "timetk"
)
}
grid <- expand.grid(
col = col_nms,
lag_val = .lags,
diff_val = .differences,
stringsAsFactors = FALSE
)
calls <- purrr::pmap(.l = list(grid$col, grid$lag_val, grid$diff_val), make_call)
if (any(.names == "auto")) {
newname <- paste0(grid$col, "_lag", grid$lag_val, "_diff", grid$diff_val)
} else {
newname <- as.list(.names)
}
calls <- purrr::set_names(calls, newname)
ret <- tibble::as_tibble(dplyr::mutate(.data, !!!calls))
return(ret)
}
#' @export
tk_augment_differences.grouped_df <- function(.data,
.value,
.lags = 1,
.differences = 1,
.log = FALSE,
.names = "auto") {
# Tidy Eval Setup
column_expr <- enquo(.value)
group_names <- dplyr::group_vars(.data)
.data %>%
tidyr::nest() %>%
dplyr::mutate(nested.col = purrr::map(
.x = data,
.f = function(df) tk_augment_differences(
.data = df,
.value = !! enquo(.value),
.lags = .lags,
.differences = .differences,
.log = .log,
.names = .names
)
)) %>%
dplyr::select(-"data") %>%
tidyr::unnest(cols = nested.col) %>%
dplyr::group_by_at(.vars = group_names)
}
#' @export
tk_augment_differences.default <- function(.data,
.value,
.lags = 1,
.differences = 1,
.log = FALSE,
.names = "auto") {
stop(paste0("`tk_augment_differences` has no method for class ", class(data)[[1]]))
}
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