R/geom_half_circle.R

In erocoar/vetoboxr: Spatial Voting in R

#' Half-Circles with pre-defined radii.
#'
#' @section Aesthetics:
#' geom_half_circle understands the following aesthetics (required aesthetics are in bold):
#'
#' - **x** - x-coordinate of center
#' - **y** - y-coordinate of center
#' - **r** - radius
#' - color
#' - fill
#' - linetype
#' - alpha
#' @inheritParams ggplot2::layer
#' @inheritParams ggplot2::geom_polygon
#' @param n The number of points calculated for the circle polygon, defaults to 180.
#'
#' @importFrom ggplot2 layer
#'
#' @export
geom_half_circle <- function(mapping = NULL, data = NULL, stat = "half_circle",
                        position = "identity", n = 180, na.rm = FALSE,
                        show.legend = NA, inherit.aes = TRUE, ...) {
  layer(
    data = data, mapping = mapping, stat = stat, geom = GeomHalfCircle,
    position = position, show.legend = show.legend, inherit.aes = inherit.aes,
    params = list(n = n, na.rm = na.rm, ...)
  )
}

# set.seed(22189)
# df <- data.frame(x = sample(1:10, 3), y = sample(1:10, 3),
#                  r = sample(3:4, 3, replace = TRUE))
#
# ggplot(df) + geom_half_circle(aes(x = x, y = y, r = r, fill = gl(3, 1))) +
#   coord_fixed()


#' @rdname geom_half_circle
#' @format NULL
#' @usage NULL
#' @importFrom ggplot2 ggproto GeomPolygon
#' @export
GeomHalfCircle <- ggproto("GeomHalfCircle", GeomPolygon,
                      default_aes = list(colour = "black", fill = NA, size = 0.5, linetype = 1, alpha = NA)
)