Tweak&fix epi_slide docs regarding packing, nesting

R/slide.R

@@ -70,52 +70,81 @@
 #' @export
 #' @seealso [`epi_slide_opt`] for optimized slide functions
 #' @examples
+#' library(dplyr)
+#'
 #' # Get the 7-day trailing standard deviation of cases and the 7-day trailing mean of cases
 #' cases_deaths_subset %>%
 #'   epi_slide(
 #'     cases_7sd = sd(cases, na.rm = TRUE),
 #'     cases_7dav = mean(cases, na.rm = TRUE),
 #'     .window_size = 7
 #'   ) %>%
-#'   dplyr::select(geo_value, time_value, cases, cases_7sd, cases_7dav)
+#'   select(geo_value, time_value, cases, cases_7sd, cases_7dav)
+#' # Note that epi_slide_mean could be used to more quickly calculate cases_7dav.
+#'
+#' # In addition to the [`dplyr::mutate`]-like syntax, you can feed in a function or
+#' # formula in a way similar to [`dplyr::group_modify`]:
+#' my_summarizer <- function(window_data) {
+#'   window_data %>%
+#'     summarize(
+#'       cases_7sd = sd(cases, na.rm = TRUE),
+#'       cases_7dav = mean(cases, na.rm = TRUE)
+#'     )
+#' }
+#' cases_deaths_subset %>%
+#'   epi_slide(
+#'     ~ my_summarizer(.x),
+#'     .window_size = 7
+#'   ) %>%
+#'   select(geo_value, time_value, cases, cases_7sd, cases_7dav)
+#'
 #'
-#' # The same as above, but unpacking using an unnamed data.frame with a formula
+#'
+#'
+#'
+#' #### Advanced: ####
+#'
+#' # The tidyverse supports ["packing"][tidyr::pack] multiple columns into a
+#' # single tibble-type column contained within some larger tibble. Like dplyr,
+#' # we normally don't pack output columns together, but will if you provide a
+#' # name for a tibble-type output:
 #' cases_deaths_subset %>%
 #'   epi_slide(
-#'     ~ data.frame(
+#'     slide_packed = tibble(
 #'       cases_7sd = sd(.x$cases, na.rm = TRUE),
 #'       cases_7dav = mean(.x$cases, na.rm = TRUE)
 #'     ),
 #'     .window_size = 7
 #'   ) %>%
-#'   dplyr::select(geo_value, time_value, cases, cases_7sd, cases_7dav)
-#'
-#' # The same as above, but packing using a named data.frame with a tidy evaluation
-#' # expression
+#'   select(geo_value, time_value, cases, slide_packed)
 #' cases_deaths_subset %>%
 #'   epi_slide(
-#'     slide_packed = data.frame(
+#'     ~ tibble(
 #'       cases_7sd = sd(.x$cases, na.rm = TRUE),
 #'       cases_7dav = mean(.x$cases, na.rm = TRUE)
 #'     ),
+#'     .new_col_name = "slide_packed",
 #'     .window_size = 7
 #'   ) %>%
-#'   dplyr::select(geo_value, time_value, cases, slide_packed)
+#'   select(geo_value, time_value, cases, slide_packed)
 #'
-#' # nested new columns
+#' # You can also get ["nested"][tidyr::nest] format by wrapping your results in
+#' # a list:
 #' cases_deaths_subset %>%
 #'   group_by(geo_value) %>%
 #'   epi_slide(
 #'     function(x, g, t) {
-#'       data.frame(
+#'       list(tibble(
 #'         cases_7sd = sd(x$cases, na.rm = TRUE),
 #'         cases_7dav = mean(x$cases, na.rm = TRUE)
-#'       )
+#'       ))
 #'     },
 #'     .window_size = 7
 #'   ) %>%
 #'   ungroup() %>%
-#'   dplyr::select(geo_value, time_value, cases, cases_7sd, cases_7dav)
+#'   select(geo_value, time_value, slide_value)
+#'
+#'
 #'
 #' # Use the geo_value or the ref_time_value in the slide computation
 #' cases_deaths_subset %>%