Dodge points vertically

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* `geom_point()` can be dodged vertically by using 
+  `position_dodge(..., orientation = "y")` (@teunbrand, #5809).
 * Fixed bug where `na.value` was incorrectly mapped to non-`NA` values 
   (@teunbrand, #5756).
 * Fixed bug in `guide_custom()` that would throw error with `theme_void()` 

R/position-dodge.R

@@ -13,6 +13,9 @@
 #'   geoms. See the examples.
 #' @param preserve Should dodging preserve the `"total"` width of all elements
 #'    at a position, or the width of a `"single"` element?
+#' @param orientation Fallback orientation when the layer or the data does not
+#'    indicate an explicit orientation, like `geom_point()`. Can be `"x"`
+#'    (default) or `"y"`.
 #' @family position adjustments
 #' @export
 #' @examples
@@ -79,10 +82,11 @@
 #'
 #' ggplot(mtcars, aes(factor(cyl), fill = factor(vs))) +
 #'   geom_bar(position = position_dodge2(preserve = "total"))
-position_dodge <- function(width = NULL, preserve = "total") {
+position_dodge <- function(width = NULL, preserve = "total", orientation = "x") {
   ggproto(NULL, PositionDodge,
     width = width,
-    preserve = arg_match0(preserve, c("total", "single"))
+    preserve = arg_match0(preserve, c("total", "single")),
+    orientation = arg_match0(orientation, c("x", "y"))
   )
 }
 
@@ -93,8 +97,9 @@ position_dodge <- function(width = NULL, preserve = "total") {
 PositionDodge <- ggproto("PositionDodge", Position,
   width = NULL,
   preserve = "total",
+  orientation = "x",
   setup_params = function(self, data) {
-    flipped_aes <- has_flipped_aes(data)
+    flipped_aes <- has_flipped_aes(data, default = self$orientation == "y")
     data <- flip_data(data, flipped_aes)
     if (is.null(data$xmin) && is.null(data$xmax) && is.null(self$width)) {
       cli::cli_warn(c(

R/utilities.R

@@ -476,6 +476,8 @@ switch_orientation <- function(aesthetics) {
 #' @param main_is_optional Is the main axis aesthetic optional and, if not
 #'   given, set to `0`
 #' @param flip Logical. Is the layer flipped.
+#' @param default The logical value to return if no orientation can be discerned
+#'   from the data.
 #'
 #' @return `has_flipped_aes()` returns `TRUE` if it detects a layer in the other
 #' orientation and `FALSE` otherwise. `flip_data()` will return the input
@@ -492,7 +494,7 @@ switch_orientation <- function(aesthetics) {
 has_flipped_aes <- function(data, params = list(), main_is_orthogonal = NA,
                             range_is_orthogonal = NA, group_has_equal = FALSE,
                             ambiguous = FALSE, main_is_continuous = FALSE,
-                            main_is_optional = FALSE) {
+                            main_is_optional = FALSE, default = FALSE) {
   # Is orientation already encoded in data?
   if (!is.null(data$flipped_aes)) {
     not_na <- which(!is.na(data$flipped_aes))
@@ -561,8 +563,7 @@ has_flipped_aes <- function(data, params = list(), main_is_orthogonal = NA,
     }
   }
 
-  # default to no
-  FALSE
+  isTRUE(default)
 }
 #' @rdname bidirection
 #' @export

tests/testthat/test-position_dodge.R

@@ -9,3 +9,17 @@ test_that("can control whether to preserve total or individual width", {
   expect_equal(layer_data(p_total)$x, new_mapped_discrete(c(1, 1.75, 2.25)))
   expect_equal(layer_data(p_single)$x, new_mapped_discrete(c(0.75, 1.75, 2.25)))
 })
+
+test_that("position_dodge() can dodge points vertically", {
+
+  df <- data.frame(x = c(1, 2, 3, 4), y = c("a", "a", "b", "b"))
+
+  horizontal <- ggplot(df, aes(y, x, group = seq_along(x))) +
+    geom_point(position = position_dodge(width = 1, orientation = "x"))
+  vertical <- ggplot(df, aes(x, y, group = seq_along(x))) +
+    geom_point(position = position_dodge(width = 1, orientation = "y"))
+
+  expect_equal(layer_data(horizontal)$x, c(0.75, 1.25, 1.75, 2.25), ignore_attr = "class")
+  expect_equal(layer_data(vertical)$y,   c(0.75, 1.25, 1.75, 2.25), ignore_attr = "class")
+
+})