purrr style lambda notation in scale arguments (#4427)

* Add function for converting lambda formula input to functions

* Convert formula input to function for arguments that allow functions

* Mention in argument descriptions that functions can be in labmda notation

* Add unit test for lambda notation

* Fix typo

* Regenerate docs

* Add news bullet

* Update tests/testthat/test-scales.r

Co-authored-by: Hiroaki Yutani <[email protected]>

Co-authored-by: Hiroaki Yutani <[email protected]>

Author: teunbrand

NEWS.md

@@ -112,6 +112,9 @@
 
 * `ggsave()` now returns the saved file location invisibly (#3379, @eliocamp).
 
+* The scale arguments `limits`, `breaks`, `minor_breaks`, `labels`, `rescaler`
+  and `oob` now accept purrr style lambda notation (@teunbrand, #4427).
+
 # ggplot2 3.3.3
 This is a small patch release mainly intended to address changes in R and CRAN.
 It further changes the licensing model of ggplot2 to an MIT license.

R/scale-.r

@@ -18,13 +18,15 @@
 #'     [transformation object][scales::trans_new()]
 #'   - A numeric vector of positions
 #'   - A function that takes the limits as input and returns breaks
-#'     as output (e.g., a function returned by [scales::extended_breaks()])
+#'     as output (e.g., a function returned by [scales::extended_breaks()]).
+#'     Also accepts rlang [lambda][rlang::as_function()] function notation.
 #' @param minor_breaks One of:
 #'   - `NULL` for no minor breaks
 #'   - `waiver()` for the default breaks (one minor break between
 #'     each major break)
 #'   - A numeric vector of positions
-#'   - A function that given the limits returns a vector of minor breaks.
+#'   - A function that given the limits returns a vector of minor breaks. Also
+#'     accepts rlang [lambda][rlang::as_function()] function notation.
 #' @param n.breaks An integer guiding the number of major breaks. The algorithm
 #'   may choose a slightly different number to ensure nice break labels. Will
 #'   only have an effect if `breaks = waiver()`. Use `NULL` to use the default
@@ -35,24 +37,28 @@
 #'     transformation object
 #'   - A character vector giving labels (must be same length as `breaks`)
 #'   - A function that takes the breaks as input and returns labels
-#'     as output
+#'     as output. Also accepts rlang [lambda][rlang::as_function()] function
+#'     notation.
 #' @param limits One of:
 #'   - `NULL` to use the default scale range
 #'   - A numeric vector of length two providing limits of the scale.
 #'     Use `NA` to refer to the existing minimum or maximum
 #'   - A function that accepts the existing (automatic) limits and returns
-#'     new limits
+#'     new limits. Also accepts rlang [lambda][rlang::as_function()] function
+#'     notation.
 #'   Note that setting limits on positional scales will **remove** data outside of the limits.
 #'   If the purpose is to zoom, use the limit argument in the coordinate system
 #'   (see [coord_cartesian()]).
 #' @param rescaler A function used to scale the input values to the
 #'   range \[0, 1]. This is always [scales::rescale()], except for
 #'   diverging and n colour gradients (i.e., [scale_colour_gradient2()],
 #'   [scale_colour_gradientn()]). The `rescaler` is ignored by position
-#'   scales, which always use [scales::rescale()].
+#'   scales, which always use [scales::rescale()]. Also accepts rlang
+#'   [lambda][rlang::as_function()] function notation.
 #' @param oob One of:
 #'   - Function that handles limits outside of the scale limits
-#'   (out of bounds).
+#'   (out of bounds). Also accepts rlang [lambda][rlang::as_function()]
+#'   function notation.
 #'   - The default ([scales::censor()]) replaces out of
 #'   bounds values with `NA`.
 #'   - [scales::squish()] for squishing out of bounds values into range.
@@ -104,6 +110,14 @@ continuous_scale <- function(aesthetics, scale_name, palette, name = waiver(),
     limits <- trans$transform(limits)
   }
 
+  # Convert formula to function if appropriate
+  limits   <- allow_lambda(limits)
+  breaks   <- allow_lambda(breaks)
+  labels   <- allow_lambda(labels)
+  rescaler <- allow_lambda(rescaler)
+  oob      <- allow_lambda(oob)
+  minor_breaks <- allow_lambda(minor_breaks)
+
   ggproto(NULL, super,
     call = match.call(),
 
@@ -142,13 +156,15 @@ continuous_scale <- function(aesthetics, scale_name, palette, name = waiver(),
 #'   - `waiver()` for the default breaks (the scale limits)
 #'   - A character vector of breaks
 #'   - A function that takes the limits as input and returns breaks
-#'     as output
+#'     as output. Also accepts rlang [lambda][rlang::as_function()] function
+#'     notation.
 #' @param limits One of:
 #'   - `NULL` to use the default scale values
 #'   - A character vector that defines possible values of the scale and their
 #'     order
 #'   - A function that accepts the existing (automatic) values and returns
-#'     new ones
+#'     new ones. Also accepts rlang [lambda][rlang::as_function()] function
+#'     notation.
 #' @param drop Should unused factor levels be omitted from the scale?
 #'    The default, `TRUE`, uses the levels that appear in the data;
 #'    `FALSE` uses all the levels in the factor.
@@ -168,6 +184,11 @@ discrete_scale <- function(aesthetics, scale_name, palette, name = waiver(),
 
   check_breaks_labels(breaks, labels)
 
+  # Convert formula input to function if appropriate
+  limits <- allow_lambda(limits)
+  breaks <- allow_lambda(breaks)
+  labels <- allow_lambda(labels)
+
   if (!is.function(limits) && (length(limits) > 0) && !is.discrete(limits)) {
     warn(
       glue(
@@ -217,7 +238,7 @@ discrete_scale <- function(aesthetics, scale_name, palette, name = waiver(),
 #'   instead of exactly evenly spaced between the limits. If `TRUE` (default)
 #'   the scale will ask the transformation object to create breaks, and this
 #'   may result in a different number of breaks than requested. Ignored if
-#'   breaks are given explicetly.
+#'   breaks are given explicitly.
 #' @param right Should values on the border between bins be part of the right
 #'   (upper) bin?
 #' @param show.limits should the limits of the scale appear as ticks
@@ -244,6 +265,13 @@ binned_scale <- function(aesthetics, scale_name, palette, name = waiver(),
     limits <- trans$transform(limits)
   }
 
+  # Convert formula input to function if appropriate
+  limits   <- allow_lambda(limits)
+  breaks   <- allow_lambda(breaks)
+  labels   <- allow_lambda(labels)
+  rescaler <- allow_lambda(rescaler)
+  oob      <- allow_lambda(oob)
+
   ggproto(NULL, super,
     call = match.call(),
 
@@ -1167,3 +1195,7 @@ check_transformation <- function(x, transformed, name, axis) {
 trans_support_nbreaks <- function(trans) {
   "n" %in% names(formals(trans$breaks))
 }
+
+allow_lambda <- function(x) {
+  if (is_formula(x)) as_function(x) else x
+}