documentation improvements and clarifications

Co-authored-by: brookslogan <lcbrooks@cs.cmu.edu>

Author: nmdefries

R/methods-epi_archive.R

@@ -661,10 +661,10 @@ group_by.epi_archive = function(.data, ..., .add=FALSE, .drop=dplyr::group_by_dr
 #'   column names as the archive's `DT`, minus the `version` column; followed
 #'   by a one-row tibble containing the values of the grouping variables for
 #'   the associated group; followed by a Date containing the reference time
-#'   value to use; followed by any number of named arguments. If a formula,
-#'   `f` can operate directly on columns accessed via `.x$var` or `.`, as in
+#'   value that was used; followed by any number of named arguments. If a formula,
+#'   `f` can operate directly on columns accessed via `.x$var` or `.$var`, as in
 #'   `~ mean (.x$var)` to compute a mean of a column `var` for each
-#'   `ref_time_value`-group combination. The group key can be accessed via
+#'   group-`ref_time_value` combination. The group key can be accessed via
 #'   `.y` or `.group_key`, and the reference time value can be accessed via
 #'   `.z` or `.ref_time_value`. If `f` is missing, then `...` will specify
 #'   the computation.

R/slide.R

@@ -14,7 +14,7 @@
 #'   step is typically one day or one week; see details for more explanation. If
 #'   a function, `f` must take a data frame with the same column names as
 #'   the original object, minus any grouping variables, containing the time
-#'   window data for one `ref_time_value`-group combination; followed by a
+#'   window data for one group-`ref_time_value` combination; followed by a
 #'   one-row tibble containing the values of the grouping variables for the
 #'   associated group; followed by any number of named arguments. If a formula,
 #'   `f` can operate directly on columns accessed via `.x$var` or `.$var`, as

R/utils.R

@@ -190,21 +190,21 @@ assert_sufficient_f_args <- function(f, ..., n_mandatory_f_args = 2L) {
 #' This powers the lambda syntax in packages like purrr.
 #'
 #' This is an extension of `rlang::as_function` that can create functions that
-#' take three arguments. The arugments can be accessed via the idiomatic
+#' take three arguments. The arguments can be accessed via the idiomatic
 #' `.x`, `.y`, etc, positional references (`..1`, `..2`, etc), and also by
 #' `slide`-specific names.
 #'
 #' @param x A function or formula.
 #'
 #'   If a **function**, it is used as is.
 #'
-#'   If a **formula**, e.g. `~ .x + 2`, it is converted to a function with up
+#'   If a **formula**, e.g. `~ mean(.x$cases)`, it is converted to a function with up
 #'   to three arguments: `.x` (single argument), or `.x` and `.y`
 #'   (two arguments), or `.x`, `.y`, and `.z` (three arguments). The `.`
 #'   placeholder can be used instead of `.x`, `.group_key` can be used in
 #'   place of `.y`, and `.ref_time_value` can be used in place of `.z`. This
 #'   allows you to create very compact anonymous functions (lambdas) with up
-#'   to two inputs. Functions created from formulas have a special class. Use
+#'   to three inputs. Functions created from formulas have a special class. Use
 #'   `rlang::is_lambda()` to test for it.
 #'
 #'   If a **string**, the function is looked up in `env`. Note that