From 80c5028708748b21d6c7b9baab9acbfc380adc6b Mon Sep 17 00:00:00 2001
From: aijordan <aijordan@users.noreply.github.com>
Date: Thu, 22 Jul 2021 15:57:01 +0200
Subject: [PATCH 1/2] `stat_bin()` accepts functions for argument `breaks`

---
 R/stat-bin.R                   | 5 ++++-
 man/geom_histogram.Rd          | 2 +-
 tests/testthat/test-stat-bin.R | 8 ++++++++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/R/stat-bin.R b/R/stat-bin.R
index 4f35d83a84..4c00b2e3ab 100644
--- a/R/stat-bin.R
+++ b/R/stat-bin.R
@@ -22,7 +22,7 @@
 #'   outside the range of the data.
 #' @param breaks Alternatively, you can supply a numeric vector giving
 #'    the bin boundaries. Overrides `binwidth`, `bins`, `center`,
-#'    and `boundary`.
+#'    and `boundary`. Can also be a function that takes group-wise values as input and returns bin boundaries.
 #' @param closed One of `"right"` or `"left"` indicating whether right
 #'   or left edges of bins are included in the bin.
 #' @param pad If `TRUE`, adds empty bins at either end of x. This ensures
@@ -146,6 +146,9 @@ StatBin <- ggproto("StatBin", Stat,
                            origin = NULL, right = NULL, drop = NULL) {
     x <- flipped_names(flipped_aes)$x
     if (!is.null(breaks)) {
+      if (is.function(breaks)) {
+        breaks <- breaks(data[[x]])
+      }
       if (!scales[[x]]$is_discrete()) {
          breaks <- scales[[x]]$transform(breaks)
       }
diff --git a/man/geom_histogram.Rd b/man/geom_histogram.Rd
index 7cd907daed..f60ec4b1f5 100644
--- a/man/geom_histogram.Rd
+++ b/man/geom_histogram.Rd
@@ -164,7 +164,7 @@ outside the range of the data.}
 
 \item{breaks}{Alternatively, you can supply a numeric vector giving
 the bin boundaries. Overrides \code{binwidth}, \code{bins}, \code{center},
-and \code{boundary}.}
+and \code{boundary}. Can also be a function that takes group-wise values as input and returns bin boundaries.}
 
 \item{closed}{One of \code{"right"} or \code{"left"} indicating whether right
 or left edges of bins are included in the bin.}
diff --git a/tests/testthat/test-stat-bin.R b/tests/testthat/test-stat-bin.R
index af0ae467f3..9b55054604 100644
--- a/tests/testthat/test-stat-bin.R
+++ b/tests/testthat/test-stat-bin.R
@@ -60,6 +60,14 @@ test_that("can use breaks argument", {
   expect_equal(out$count, c(1, 2))
 })
 
+test_that("breaks computes bin boundaries for function input", {
+  df <- data.frame(x = c(0, 0, 0, 1:3))
+  out <- layer_data(ggplot(df, aes(x)) +
+                      geom_histogram(breaks = function(x) c(0, 0.5, 2.5, 7.5)))
+
+  expect_equal(out$count, c(3, 2, 1))
+})
+
 test_that("fuzzy breaks are used when cutting", {
   df <- data_frame(x = c(-1, -0.5, -0.4, 0))
   p <- ggplot(df, aes(x)) +

From dbba2cfbf1674c8f2d68c554e4e042c13a7ab1d7 Mon Sep 17 00:00:00 2001
From: aijordan <aijordan@users.noreply.github.com>
Date: Fri, 28 Jun 2024 19:01:07 +0200
Subject: [PATCH 2/2] add news bullet

---
 NEWS.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/NEWS.md b/NEWS.md
index e99235a3a0..d553c7f924 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,6 @@
 # ggplot2 (development version)
 
+* `stat_bin()` now accepts functions for argument `breaks` (@aijordan, #4561)
 * (internal) The plot's layout now has a coord parameter that is used to 
   prevent setting up identical panel parameters (#5427)
 * (internal) rearranged the code of `Facet$draw_panels()` method (@teunbrand).