From 3c23e31c66bbeeae31974a74a7abb371172e228a Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 19:38:07 +0100
Subject: [PATCH 1/9] Add polar bounding box calculation

---
 R/coord-polar.r                   | 27 +++++++++++++++++++++++++++
 tests/testthat/test-coord-polar.r | 24 ++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index 61d74e31ab..89072049ed 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -312,3 +312,30 @@ r_rescale <- function(coord, x, range) {
   x <- squish_infinite(x, range)
   rescale(x, c(0, 0.4), range)
 }
+
+# Calculate bounding box for the sector of the circle
+# Takes `theta_range` as a vector of two angles in radians
+polar_bbox <- function(theta_range) {
+
+  # X and Y positions of the sector arc ends
+  x <- 0.5 * sin(theta_range) + 0.5
+  y <- 0.5 * cos(theta_range) + 0.5
+
+  # Check for top, right, bottom and left if it falls in sector
+  pos_theta <- seq(0, 1.5 * pi, length.out = 4)
+  theta_range <- theta_range %% (2 * pi)
+
+  in_sector <- if (theta_range[1] < theta_range[2]) {
+      pos_theta >= theta_range[1] & pos_theta <= theta_range[2]
+  } else {
+    !(pos_theta <  theta_range[1] & pos_theta >  theta_range[2])
+  }
+
+  # If position is in sector, take extreme bounds
+  # If not, choose center (+/- 0.05 buffer) or sector arc ends
+  bounds <- ifelse(
+    in_sector,
+    c(1, 1, 0, 0),
+    c(max(y, 0.55), max(x, 0.55), min(y, 0.45), min(x, 0.45))
+  )
+  list(x = c(bounds[4], bounds[2]), y = c(bounds[3], bounds[1]))
diff --git a/tests/testthat/test-coord-polar.r b/tests/testthat/test-coord-polar.r
index f1570b6a96..45c0bdd63a 100644
--- a/tests/testthat/test-coord-polar.r
+++ b/tests/testthat/test-coord-polar.r
@@ -79,6 +79,30 @@ test_that("Inf is squished to range", {
   expect_equal(d[[3]]$theta, mapped_discrete(0))
 })
 
+test_that("polar_bbox() gives correct bounds", {
+
+  # Full circle
+  bounds <- polar_bbox(c(0, 2 * pi))
+  expect_equal(bounds, list(x = c(0, 1), y = c(0, 1)))
+
+  # Overshoot
+  bounds <- polar_bbox(c(-3, 3) * pi)
+  expect_equal(bounds, list(x = c(0, 1), y = c(0, 1)))
+
+  # Half circle
+  bounds <- polar_bbox(c(0.5, 1.5) * pi)
+  expect_equal(bounds, list(x = c(0, 1), y = c(0, 0.55)))
+
+  # Quarter circle
+  bounds <- polar_bbox(c(0, 0.5 * pi))
+  expect_equal(bounds, list(x = c(0.45, 1), y = c(0.45, 1)))
+
+  # Quarter circle at 45 degrees
+  bounds <- polar_bbox(c(0.25, 0.75) * pi)
+  expect_equal(bounds, list(x = c(0.45, 1),
+                            y = 0.5 + cos(c(0.75, 0.25) * pi) * 0.5))
+
+})
 
 # Visual tests ------------------------------------------------------------
 

From aa482777527933b4b0a7fece5071d8acb3147ac2 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 19:50:49 +0100
Subject: [PATCH 2/9] Apply arc transform

---
 R/coord-polar.r | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index 89072049ed..b025236f82 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -58,14 +58,15 @@
 #' doh + geom_bar(width = 0.9, position = "fill") + coord_polar(theta = "y")
 #' }
 #' }
-coord_polar <- function(theta = "x", start = 0, direction = 1, clip = "on") {
+coord_polar <- function(theta = "x", start = 0, end = 2 * pi,
+                        direction = 1, clip = "on") {
   theta <- arg_match0(theta, c("x", "y"))
   r <- if (theta == "x") "y" else "x"
 
   ggproto(NULL, CoordPolar,
     theta = theta,
     r = r,
-    start = start,
+    arc = c(start, end),
     direction = sign(direction),
     clip = clip
   )
@@ -198,7 +199,7 @@ CoordPolar <- ggproto("CoordPolar", Coord,
       theta_rescale(self, panel_params$theta.major, panel_params)
     thetamin <- if (length(panel_params$theta.minor) > 0)
       theta_rescale(self, panel_params$theta.minor, panel_params)
-    thetafine <- seq(0, 2 * pi, length.out = 100)
+    thetafine <- seq(self$arc[1], self$arc[2], length.out = 100)
 
     rfine <- c(r_rescale(self, panel_params$r.major, panel_params$r.range), 0.45)
 
@@ -298,14 +299,16 @@ rename_data <- function(coord, data) {
 }
 
 theta_rescale_no_clip <- function(coord, x, panel_params) {
-  rotate <- function(x) (x + coord$start) * coord$direction
-  rotate(rescale(x, c(0, 2 * pi), panel_params$theta.range))
+  arc <- coord$arc %||% c(0, 2 * pi)
+  rotate <- function(x) x * coord$direction
+  rotate(rescale(x, arc, panel_params$theta.range))
 }
 
 theta_rescale <- function(coord, x, panel_params) {
+  arc <- coord$arc %||% c(0, 2 * pi)
   x <- squish_infinite(x, panel_params$theta.range)
-  rotate <- function(x) (x + coord$start) %% (2 * pi) * coord$direction
-  rotate(rescale(x, c(0, 2 * pi), panel_params$theta.range))
+  rotate <- function(x) x %% (2 * pi) * coord$direction
+  rotate(rescale(x, arc, panel_params$theta.range))
 }
 
 r_rescale <- function(coord, x, range) {
@@ -339,3 +342,4 @@ polar_bbox <- function(theta_range) {
     c(max(y, 0.55), max(x, 0.55), min(y, 0.45), min(x, 0.45))
   )
   list(x = c(bounds[4], bounds[2]), y = c(bounds[3], bounds[1]))
+}

From cd12d6c9394aaa5ce71fc935a1296a7e7b453ea9 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 20:12:25 +0100
Subject: [PATCH 3/9] Apply bounding box rescale

---
 R/coord-polar.r | 54 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 42 insertions(+), 12 deletions(-)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index b025236f82..050fa78874 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -78,7 +78,9 @@ coord_polar <- function(theta = "x", start = 0, end = 2 * pi,
 #' @export
 CoordPolar <- ggproto("CoordPolar", Coord,
 
-  aspect = function(details) 1,
+  aspect = function(details) {
+    diff(details$bbox$y) / diff(details$bbox$x)
+  },
 
   distance = function(self, x, y, details) {
     if (self$theta == "x") {
@@ -139,7 +141,8 @@ CoordPolar <- ggproto("CoordPolar", Coord,
       x.sec.range = ret$x$sec.range, y.sec.range = ret$y$sec.range,
       x.sec.major = ret$x$sec.major, y.sec.major = ret$y$sec.major,
       x.sec.minor = ret$x$sec.minor, y.sec.minor = ret$y$sec.minor,
-      x.sec.labels = ret$x$sec.labels, y.sec.labels = ret$y$sec.labels
+      x.sec.labels = ret$x$sec.labels, y.sec.labels = ret$y$sec.labels,
+      bbox = polar_bbox(self$arc)
     )
 
     if (self$theta == "y") {
@@ -160,8 +163,14 @@ CoordPolar <- ggproto("CoordPolar", Coord,
 
     data$r  <- r_rescale(self, data$r, panel_params$r.range)
     data$theta <- theta_rescale(self, data$theta, panel_params)
-    data$x <- data$r * sin(data$theta) + 0.5
-    data$y <- data$r * cos(data$theta) + 0.5
+    data$x <- rescale(
+      data$r * sin(data$theta) + 0.5,
+      from = panel_params$bbox$x
+    )
+    data$y <- rescale(
+      data$r * cos(data$theta) + 0.5,
+      from = panel_params$bbox$y
+    )
 
     data
   },
@@ -213,23 +222,41 @@ CoordPolar <- ggproto("CoordPolar", Coord,
       element_render(theme, "panel.background"),
       if (length(theta) > 0) element_render(
         theme, majortheta, name = "angle",
-        x = vec_interleave(0, 0.45 * sin(theta)) + 0.5,
-        y = vec_interleave(0, 0.45 * cos(theta)) + 0.5,
+        x = rescale(
+          vec_interleave(0, 0.45 * sin(theta)) + 0.5,
+          from = panel_params$bbox$x
+        ),
+        y = rescale(
+          vec_interleave(0, 0.45 * cos(theta)) + 0.5,
+          from = panel_params$bbox$y
+        ),
         id.lengths = rep(2, length(theta)),
         default.units = "native"
       ),
       if (length(thetamin) > 0) element_render(
         theme, minortheta, name = "angle",
-        x = vec_interleave(0, 0.45 * sin(thetamin)) + 0.5,
-        y = vec_interleave(0, 0.45 * cos(thetamin)) + 0.5,
+        x = rescale(
+          vec_interleave(0, 0.45 * sin(thetamin)) + 0.5,
+          from = panel_params$bbox$x
+        ),
+        y = rescale(
+          vec_interleave(0, 0.45 * cos(thetamin)) + 0.5,
+          from = panel_params$bbox$y
+        ),
         id.lengths = rep(2, length(thetamin)),
         default.units = "native"
       ),
 
       element_render(
         theme, majorr, name = "radius",
-        x = rep(rfine, each = length(thetafine)) * rep(sin(thetafine), length(rfine)) + 0.5,
-        y = rep(rfine, each = length(thetafine)) * rep(cos(thetafine), length(rfine)) + 0.5,
+        x = rescale(
+          as.vector(outer(sin(thetafine), rfine)) + 0.5,
+          from = panel_params$bbox$x
+        ),
+        y = rescale(
+          as.vector(outer(cos(thetafine), rfine)) + 0.5,
+          from = panel_params$bbox$y
+        ),
         id.lengths = rep(length(thetafine), length(rfine)),
         default.units = "native"
       )
@@ -260,12 +287,15 @@ CoordPolar <- ggproto("CoordPolar", Coord,
       theta <- theta[-1]
     }
 
+    x <- rescale(0.45 * sin(theta) + 0.5, from = panel_params$bbox$x)
+    y <- rescale(0.45 * cos(theta) + 0.5, from = panel_params$bbox$y)
+
     grobTree(
       if (length(labels) > 0) element_render(
         theme, "axis.text.x",
         labels,
-        unit(0.45 * sin(theta) + 0.5, "native"),
-        unit(0.45 * cos(theta) + 0.5, "native"),
+        unit(x, "native"),
+        unit(y, "native"),
         hjust = 0.5, vjust = 0.5
       ),
       element_render(theme, "panel.border")

From b30e79821c8390dea3cffb999190a682c5e3cc98 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 21:55:51 +0100
Subject: [PATCH 4/9] Fix axis placement

---
 R/coord-polar.r | 102 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 88 insertions(+), 14 deletions(-)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index 050fa78874..0814ef4469 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -142,7 +142,8 @@ CoordPolar <- ggproto("CoordPolar", Coord,
       x.sec.major = ret$x$sec.major, y.sec.major = ret$y$sec.major,
       x.sec.minor = ret$x$sec.minor, y.sec.minor = ret$y$sec.minor,
       x.sec.labels = ret$x$sec.labels, y.sec.labels = ret$y$sec.labels,
-      bbox = polar_bbox(self$arc)
+      bbox = polar_bbox(self$arc),
+      arc  = self$arc
     )
 
     if (self$theta == "y") {
@@ -176,6 +177,16 @@ CoordPolar <- ggproto("CoordPolar", Coord,
   },
 
   render_axis_v = function(self, panel_params, theme) {
+
+    place_axis <- in_arc(c(0, 1) * pi, panel_params$arc)
+    if (!any(place_axis)) {
+      ans <- list(
+        left  = draw_axis(NA, "", "left", theme),
+        right = zeroGrob()
+      )
+      return(ans)
+    }
+
     arrange <- panel_params$r.arrange %||% c("primary", "secondary")
 
     x <- r_rescale(self, panel_params$r.major, panel_params$r.range) + 0.5
@@ -188,17 +199,77 @@ CoordPolar <- ggproto("CoordPolar", Coord,
       ) + 0.5
     }
 
+    if (!place_axis[1]) {
+      panel_params$r.major <- 1 - panel_params$r.major
+      if (!is.null(panel_params$r.sec.major)) {
+        panel_params$r.sec.major <- 1 - panel_params$r.sec.major
+      }
+    }
+
+    panel_params$r.major <- rescale(panel_params$r.major,
+                                    from = panel_params$bbox$y)
+    panel_params$r.sec.major <- rescale(panel_params$r.sec.major,
+                                        from = panel_params$bbox$y)
+
     list(
-      left = render_axis(panel_params, arrange[1], "r", "left", theme),
+      left  = render_axis(panel_params, arrange[1], "r", "left", theme),
       right = render_axis(panel_params, arrange[2], "r", "right", theme)
     )
   },
 
   render_axis_h = function(panel_params, theme) {
-    list(
+
+    no_axis <- list(
       top = zeroGrob(),
       bottom = draw_axis(NA, "", "bottom", theme)
     )
+
+    # Return no axis if there should already be a left/right axis
+    if (any(in_arc(c(0, 1) * pi, panel_params$arc))) {
+      return(no_axis)
+    }
+
+    place_axis <- in_arc(c(0.5, 1.5) * pi, panel_params$arc)
+    if (!any(place_axis)) {
+      # This should in theory never happen
+      cli::cli_inform(c(paste0(
+        "Could not find appropriate placement for the {.field radius}",
+        " axis."
+      ), i = paste0(
+        "A {.field radius} axis requires the [{.arg start}-{.arg end}] range to ",
+        "include one of: {.code c(0, 0.5, 1, 1.5) * pi}."
+      )))
+      return(no_axis)
+    }
+
+    arrange <- panel_params$r.arrange %||% c("primary", "secondary")
+
+    y <- r_rescale(self, panel_params$r.major, panel_params$r.range) + 0.5
+    panel_params$r.major <- y
+    if (!is.null(panel_params$r.sec.major)) {
+      panel_params$r.sec.major <- r_rescale(
+        self,
+        panel_params$r.sec.major,
+        panel_params$r.sec.range
+      ) + 0.5
+    }
+
+    if (!place_axis[1]) {
+      panel_params$r.major <- 1 - panel_params$r.major
+      if (!is.null(panel_params$r.sec.major)) {
+        panel_params$r.sec.major <- 1 - panel_params$r.sec.major
+      }
+    }
+
+    panel_params$r.major <- rescale(panel_params$r.major,
+                                    from = panel_params$bbox$x)
+    panel_params$r.sec.major <- rescale(panel_params$r.sec.major,
+                                        from = panel_params$bbox$x)
+
+    list(
+      top     = render_axis(panel_params, arrange[2], "r", "top", theme),
+      bottom  = render_axis(panel_params, arrange[1], "r", "bottom", theme)
+    )
   },
 
   render_bg = function(self, panel_params, theme) {
@@ -347,22 +418,16 @@ r_rescale <- function(coord, x, range) {
 }
 
 # Calculate bounding box for the sector of the circle
-# Takes `theta_range` as a vector of two angles in radians
-polar_bbox <- function(theta_range) {
+# Takes `arc` as a vector of two angles in radians
+polar_bbox <- function(arc) {
 
   # X and Y positions of the sector arc ends
-  x <- 0.5 * sin(theta_range) + 0.5
-  y <- 0.5 * cos(theta_range) + 0.5
+  x <- 0.5 * sin(arc) + 0.5
+  y <- 0.5 * cos(arc) + 0.5
 
   # Check for top, right, bottom and left if it falls in sector
   pos_theta <- seq(0, 1.5 * pi, length.out = 4)
-  theta_range <- theta_range %% (2 * pi)
-
-  in_sector <- if (theta_range[1] < theta_range[2]) {
-      pos_theta >= theta_range[1] & pos_theta <= theta_range[2]
-  } else {
-    !(pos_theta <  theta_range[1] & pos_theta >  theta_range[2])
-  }
+  in_sector <- in_arc(pos_theta, arc)
 
   # If position is in sector, take extreme bounds
   # If not, choose center (+/- 0.05 buffer) or sector arc ends
@@ -373,3 +438,12 @@ polar_bbox <- function(theta_range) {
   )
   list(x = c(bounds[4], bounds[2]), y = c(bounds[3], bounds[1]))
 }
+
+in_arc <- function(theta, arc) {
+  arc <- arc %% (2 * pi)
+  if (arc[1] < arc[2]) {
+      theta >= arc[1] & theta <= arc[2]
+  } else {
+    !(theta <  arc[1] & theta >  arc[2])
+  }
+}

From 4db3391c0e115426badb1148c89a8d088a1f391d Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 22:08:14 +0100
Subject: [PATCH 5/9] Sync start/end

---
 R/coord-polar.r | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index 0814ef4469..6e77aa69f9 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -63,6 +63,11 @@ coord_polar <- function(theta = "x", start = 0, end = 2 * pi,
   theta <- arg_match0(theta, c("x", "y"))
   r <- if (theta == "x") "y" else "x"
 
+  if (start > end) {
+    n_rotate <- ((start - end) %/% (2 * pi)) + 1
+    start <- start - n_rotate * 2 * pi
+  }
+
   ggproto(NULL, CoordPolar,
     theta = theta,
     r = r,
@@ -447,3 +452,4 @@ in_arc <- function(theta, arc) {
     !(theta <  arc[1] & theta >  arc[2])
   }
 }
+

From c54f41e3fb9771c11eb3caa6f1dc90443415141c Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 22:08:27 +0100
Subject: [PATCH 6/9] axis placement tests

---
 tests/testthat/test-coord-polar.r | 77 +++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

diff --git a/tests/testthat/test-coord-polar.r b/tests/testthat/test-coord-polar.r
index 45c0bdd63a..f2959f898c 100644
--- a/tests/testthat/test-coord-polar.r
+++ b/tests/testthat/test-coord-polar.r
@@ -104,6 +104,83 @@ test_that("polar_bbox() gives correct bounds", {
 
 })
 
+test_that("axis placement is appropriate", {
+
+  p <- ggplot_build(
+    ggplot(data.frame(x = 1:4), aes(x, x)) +
+      geom_point() +
+      scale_y_continuous(breaks = 1:4) +
+      coord_polar() +
+      theme_test()
+  )
+
+  get_breaks <- function(axis, var = "x") {
+    is_gt <- which(vapply(axis$children, inherits, logical(1), "gtable"))
+    if (length(is_gt) == 0) {
+      return(NULL)
+    }
+    axis <- axis$children[[is_gt[[1]]]]
+    is_txt <- which(vapply(axis$grobs, inherits, logical(1), "titleGrob"))
+    if (length(is_txt) == 0) {
+      return(NULL)
+    }
+    axis <- axis$grobs[[is_txt[[1]]]]
+    if (length(axis$children) == 0) {
+      return(NULL)
+    }
+    axis <- axis$children[[1]]
+    as.numeric(axis[[var]])
+  }
+
+  params <- p$layout$panel_params[[1]]
+  breaks <- (0:3/3) * 0.4 + 0.5
+
+  # Full circle, should have left axis
+  axis_h <- p$layout$coord$render_axis_h(params, p$plot$theme)
+  axis_v <- p$layout$coord$render_axis_v(params, p$plot$theme)
+
+  expect_null(get_breaks(axis_h$top, "x"))
+  expect_equal(get_breaks(axis_h$bottom, "x"), NA_real_)
+  expect_equal(get_breaks(axis_v$left, "y"), breaks)
+  expect_null(get_breaks(axis_v$right, "y"))
+
+  # Bottom half-circle, should have reverse y-axis
+  params$arc <- c(0.5, 1.5) * pi
+  axis_h <- p$layout$coord$render_axis_h(params, p$plot$theme)
+  axis_v <- p$layout$coord$render_axis_v(params, p$plot$theme)
+
+  expect_null(get_breaks(axis_h$top, "x"))
+  expect_equal(get_breaks(axis_h$bottom, "x"), NA_real_)
+  expect_equal(get_breaks(axis_v$left, "y"), 1 - breaks) # opposite
+  expect_null(get_breaks(axis_v$right, "y"))
+
+  # Right quarter circle, should have x-axis
+  params$arc <- c(0.25, 0.75) * pi
+  axis_h <- p$layout$coord$render_axis_h(params, p$plot$theme)
+  axis_v <- p$layout$coord$render_axis_v(params, p$plot$theme)
+
+  expect_null(get_breaks(axis_h$top, "x"))
+  expect_equal(get_breaks(axis_h$bottom, "x"), breaks)
+  expect_equal(get_breaks(axis_v$left, "y"), NA_real_)
+  expect_null(get_breaks(axis_v$right, "y"))
+
+  # Left quarter circle, should have reverse x-axis
+  params$arc <- c(1.25, 1.75) * pi
+  axis_h <- p$layout$coord$render_axis_h(params, p$plot$theme)
+  axis_v <- p$layout$coord$render_axis_v(params, p$plot$theme)
+
+  expect_null(get_breaks(axis_h$top, "x"))
+  expect_equal(get_breaks(axis_h$bottom, "x"), 1 - breaks)
+  expect_equal(get_breaks(axis_v$left, "y"), NA_real_)
+  expect_null(get_breaks(axis_v$right, "y"))
+
+  params$arc <- c(0.1, 0.4) * pi
+  expect_message(
+    p$layout$coord$render_axis_h(params, p$plot$theme),
+    "appropriate placement"
+  )
+})
+
 # Visual tests ------------------------------------------------------------
 
 test_that("polar coordinates draw correctly", {

From 7b286038fc4838268bb0f4478c1d7127af8d19ff Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 22:28:48 +0100
Subject: [PATCH 7/9] `end` defaults to `start + 2 * pi`

---
 R/coord-polar.r | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index 6e77aa69f9..7b7be2116b 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -58,11 +58,12 @@
 #' doh + geom_bar(width = 0.9, position = "fill") + coord_polar(theta = "y")
 #' }
 #' }
-coord_polar <- function(theta = "x", start = 0, end = 2 * pi,
+coord_polar <- function(theta = "x", start = 0, end = NULL,
                         direction = 1, clip = "on") {
   theta <- arg_match0(theta, c("x", "y"))
   r <- if (theta == "x") "y" else "x"
 
+  end <- end %||% (start + 2 * pi)
   if (start > end) {
     n_rotate <- ((start - end) %/% (2 * pi)) + 1
     start <- start - n_rotate * 2 * pi

From 2af137f970367b571ab7e2c780b6cdfdc1a85d8c Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 22:45:59 +0100
Subject: [PATCH 8/9] Fix axis title placement

---
 R/coord-polar.r | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index 7b7be2116b..f910cc6553 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -381,10 +381,17 @@ CoordPolar <- ggproto("CoordPolar", Coord,
 
   labels = function(self, labels, panel_params) {
     if (self$theta == "y") {
-      list(x = labels$y, y = labels$x)
+      if (any(in_arc(c(0, 1) * pi, self$arc))) {
+        labels <- list(x = labels$y, y = labels$x)
+      } else {
+        labels <- list(x = rev(labels$x), y = rev(labels$y))
+      }
     } else {
-      labels
+      if (!any(in_arc(c(0, 1) * pi, self$arc))) {
+        labels <- list(x = rev(labels$y), y = rev(labels$x))
+      }
     }
+    labels
   },
 
   modify_scales = function(self, scales_x, scales_y) {

From d39364617d322c9f73ecd0c2801991300efba4ac Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Thu, 3 Nov 2022 22:52:24 +0100
Subject: [PATCH 9/9] Document `end`

---
 R/coord-polar.r    | 5 +++++
 man/coord_polar.Rd | 8 +++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/R/coord-polar.r b/R/coord-polar.r
index f910cc6553..61e524f3c8 100644
--- a/R/coord-polar.r
+++ b/R/coord-polar.r
@@ -6,6 +6,8 @@
 #' @param theta variable to map angle to (`x` or `y`)
 #' @param start Offset of starting point from 12 o'clock in radians. Offset
 #'   is applied clockwise or anticlockwise depending on value of `direction`.
+#' @param end Offset of end point from 12 o'clock in radians. Can be used to
+#'   make partial polar plots. Defaults to `start + 2 * pi`.
 #' @param direction 1, clockwise; -1, anticlockwise
 #' @param clip Should drawing be clipped to the extent of the plot panel? A
 #'   setting of `"on"` (the default) means yes, and a setting of `"off"`
@@ -22,6 +24,9 @@
 #'  geom_bar(width = 1)
 #' pie + coord_polar(theta = "y")
 #'
+#' # A pie chart, but half of it is already eaten
+#' pie + coord_polar(theta = "y", start = -0.5 * pi, end = 0.5 * pi)
+#'
 #' \donttest{
 #'
 #' # A coxcomb plot = bar chart + polar coordinates
diff --git a/man/coord_polar.Rd b/man/coord_polar.Rd
index dd4d53f623..878c04ae0d 100644
--- a/man/coord_polar.Rd
+++ b/man/coord_polar.Rd
@@ -4,7 +4,7 @@
 \alias{coord_polar}
 \title{Polar coordinates}
 \usage{
-coord_polar(theta = "x", start = 0, direction = 1, clip = "on")
+coord_polar(theta = "x", start = 0, end = NULL, direction = 1, clip = "on")
 }
 \arguments{
 \item{theta}{variable to map angle to (\code{x} or \code{y})}
@@ -12,6 +12,9 @@ coord_polar(theta = "x", start = 0, direction = 1, clip = "on")
 \item{start}{Offset of starting point from 12 o'clock in radians. Offset
 is applied clockwise or anticlockwise depending on value of \code{direction}.}
 
+\item{end}{Offset of end point from 12 o'clock in radians. Can be used to
+make partial polar plots. Defaults to \code{start + 2 * pi}.}
+
 \item{direction}{1, clockwise; -1, anticlockwise}
 
 \item{clip}{Should drawing be clipped to the extent of the plot panel? A
@@ -33,6 +36,9 @@ pie <- ggplot(mtcars, aes(x = factor(1), fill = factor(cyl))) +
  geom_bar(width = 1)
 pie + coord_polar(theta = "y")
 
+# A pie chart, but half of it is already eaten
+pie + coord_polar(theta = "y", start = -0.5 * pi, end = 0.5 * pi)
+
 \donttest{
 
 # A coxcomb plot = bar chart + polar coordinates