Annotate a Polar Plot with a Coloured Wedge

This is a wrapper around ggplot2::annotate() which draws a semi-transparent wedge on a plot with continuous polar coordinates (any of polar_plot(), polar_annulus(), polar_freq() or rose_percentile()). Note that, owing to the way ggplot2::geom_col() interacts with ggplot2::coord_polar(), the .rose_angle argument should be used with rose_pollution() and rose_wind().

Usage

annotate_polar_wedge(
  start,
  end,
  fill = "red",
  colour = NA,
  alpha = 0.25,
  ...,
  .rose_angle = NULL
)

start: The angle at which to start the wedge. Can be expressed numerically, or using cardinal direction abbreviations ("N", "NNE", "NE", "ENE", etc.).
end: The angle at which to end the wedge. See end for more details.
fill: The fill colour of the wedge. Defaults to "red".
colour: The border colour of the wedge. Defaults to NA, which means no border is drawn.
alpha: The transparency of the wedge. 1 is totally opaque and 0 is completely transparent.
...: Arguments to pass to ggplot2::annotate().
.rose_angle: The number passed to the angle argument of rose_pollution()/rose_wind(). This is required to adjust start and end when they are near to North/0 due to the way ggplot2::geom_col() interacts with ggplot2::coord_polar().

An annotation to be added to ggplot2::ggplot().

if (FALSE) {
polar_plot(mydata, "nox") + annotate_polar_wedge(start = "N", end = "E")
}