Custom inside-axis position for coord_radial()

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* `coord_radial(r.axis.inside)` can now take a numeric value to control 
+ placement of internally placed radius axes (@teunbrand, #5805).
 * The `arrow.fill` parameter is now applied to more line-based functions: 
  `geom_path()`, `geom_line()`, `geom_step()` `geom_function()`, line 
  geometries in `geom_sf()` and `element_line()`.

R/coord-radial.R

@@ -7,10 +7,14 @@
 #' @param expand If `TRUE`, the default, adds a small expansion factor the
 #' the limits to prevent overlap between data and axes. If `FALSE`, limits
 #' are taken directly from the scale.
-#' @param r.axis.inside If `TRUE`, places the radius axis inside the
-#' panel. If `FALSE`, places the radius axis next to the panel. The default,
-#' `NULL`, places the radius axis outside if the `start` and `end` arguments
-#' form a full circle.
+#' @param r.axis.inside One of the following:
+#' * `NULL` (default) places the axis next to the panel if `start` and
+#' `end` arguments form a full circle and inside the panel otherwise.
+#' * `TRUE` to place the radius axis inside the panel.
+#' * `FALSE` to place the radius axis next to the panel.
+#' * A numeric value, setting a theta axis value at which
+#' the axis should be placed inside the panel. Can be given as a length 2
+#' vector to control primary and secondary axis placement separately.
 #' @param rotate.angle If `TRUE`, transforms the `angle` aesthetic in data
 #' in accordance with the computed `theta` position. If `FALSE` (default),
 #' no such transformation is performed. Can be useful to rotate text geoms in
@@ -58,7 +62,10 @@ coord_radial <- function(theta = "x",
 
  theta <- arg_match0(theta, c("x", "y"))
  r <- if (theta == "x") "y" else "x"
- check_bool(r.axis.inside, allow_null = TRUE)
+ if (!is.numeric(r.axis.inside)) {
+ check_bool(r.axis.inside, allow_null = TRUE)
+ }
+
  check_bool(expand)
  check_bool(rotate.angle)
  check_number_decimal(start, allow_infinite = FALSE)
@@ -130,12 +137,29 @@ CoordRadial <- ggproto("CoordRadial", Coord,
  },
 
  setup_panel_params = function(self, scale_x, scale_y, params = list()) {
- c(
+
+ params <- c(
  view_scales_polar(scale_x, self$theta, expand = self$expand),
  view_scales_polar(scale_y, self$theta, expand = self$expand),
  list(bbox = polar_bbox(self$arc, inner_radius = self$inner_radius),
  arc = self$arc, inner_radius = self$inner_radius)
  )
+
+ axis_rotation <- self$r_axis_inside
+ if (is.numeric(axis_rotation)) {
+ theta_scale <- switch(self$theta, x = scale_x, y = scale_y)
+ axis_rotation <- theta_scale$transform(axis_rotation)
+ axis_rotation <- oob_squish(axis_rotation, params$theta.range)
+ axis_rotation <- theta_rescale(
+ axis_rotation, params$theta.range,
+ params$arc, self$direction
+ )
+ params$axis_rotation <- rep_len(axis_rotation, length.out = 2)
+ } else {
+ params$axis_rotation <- params$arc
+ }
+
+ params
  },
 
  setup_panel_guides = function(self, panel_params, guides, params = list()) {
@@ -173,9 +197,9 @@ CoordRadial <- ggproto("CoordRadial", Coord,
  opposite_r <- isTRUE(scales$r$position %in% c("bottom", "left"))
  }
 
- if (self$r_axis_inside) {
+ if (!isFALSE(self$r_axis_inside)) {
 
- arc <- rad2deg(self$arc)
+ arc <- rad2deg(panel_params$axis_rotation)
  r_position <- c("left", "right")
  # If both opposite direction and opposite position, don't flip
  if (xor(self$direction == -1, opposite_r)) {
@@ -223,7 +247,7 @@ CoordRadial <- ggproto("CoordRadial", Coord,
  gdefs[[t]] <- guides[[t]]$get_layer_key(gdefs[[t]], layers)
  }
 
- if (self$r_axis_inside) {
+ if (!isFALSE(self$r_axis_inside)) {
  # For radial axis, we need to pretend that rotation starts at 0 and
  # the bounding box is for circles, otherwise tick positions will be
  # spaced too closely.
@@ -273,14 +297,14 @@ CoordRadial <- ggproto("CoordRadial", Coord,
  },
 
  render_axis_v = function(self, panel_params, theme) {
- if (self$r_axis_inside) {
+ if (!isFALSE(self$r_axis_inside)) {
  return(list(left = zeroGrob(), right = zeroGrob()))
  }
  CoordCartesian$render_axis_v(panel_params, theme)
  },
 
  render_axis_h = function(self, panel_params, theme) {
- if (self$r_axis_inside) {
+ if (!isFALSE(self$r_axis_inside)) {
  return(list(top = zeroGrob(), bottom = zeroGrob()))
  }
  CoordCartesian$render_axis_h(panel_params, theme)
@@ -359,7 +383,7 @@ CoordRadial <- ggproto("CoordRadial", Coord,
 
  border <- element_render(theme, "panel.border", fill = NA)
 
- if (!self$r_axis_inside) {
+ if (isFALSE(self$r_axis_inside)) {
  out <- grobTree(
  panel_guides_grob(panel_params$guides, "theta", theme),
  panel_guides_grob(panel_params$guides, "theta.sec", theme),
@@ -370,14 +394,15 @@ CoordRadial <- ggproto("CoordRadial", Coord,
 
  bbox <- panel_params$bbox
  dir <- self$direction
- arc <- if (dir == 1) self$arc else rev(self$arc)
- arc <- dir * rad2deg(-arc)
+ rot <- panel_params$axis_rotation
+ rot <- if (dir == 1) rot else rev(rot)
+ rot <- dir * rad2deg(-rot)
 
  left <- panel_guides_grob(panel_params$guides, position = "left", theme)
- left <- rotate_r_axis(left, arc[1], bbox, "left")
+ left <- rotate_r_axis(left, rot[1], bbox, "left")
 
  right <- panel_guides_grob(panel_params$guides, position = "right", theme)
- right <- rotate_r_axis(right, arc[2], bbox, "right")
+ right <- rotate_r_axis(right, rot[2], bbox, "right")
 
  grobTree(
  panel_guides_grob(panel_params$guides, "theta", theme),
@@ -426,7 +451,7 @@ CoordRadial <- ggproto("CoordRadial", Coord,
  },
 
  setup_params = function(self, data) {
- if (!self$r_axis_inside) {
+ if (isFALSE(self$r_axis_inside)) {
  place <- in_arc(c(0, 0.5, 1, 1.5) * pi, self$arc)
  if (place[1]) {
  return(list(r_axis = "left", fake_arc = c(0, 2) * pi))