#' Circle Geom
#'
#' @param n the number of circle path points.
#' @inheritParams ggplot2::layer
#' @inheritParams ggplot2::geom_polygon
#' @section Aesthetics:
#' \code{geom_circle2()} understands the following aesthetics (required aesthetics are in bold):
#' \itemize{
#' \item \strong{\code{x}}
#' \item \strong{\code{y}}
#' \item \code{r0}
#' \item \code{alpha}
#' \item \code{colour}
#' \item \code{fill}
#' \item \code{linetype}
#' \item \code{size}
#' }
#' @importFrom ggplot2 layer ggproto GeomPolygon aes
#' @importFrom grid grobTree
#' @rdname geom_circle2
#' @author Houyun Huang, Lei Zhou, Jian Chen, Taiyun Wei
#' @export
geom_circle2 <- function(mapping = NULL,
data = NULL,
stat = "identity",
position = "identity",
...,
n = 60,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE) {
layer(
data = data,
mapping = mapping,
stat = stat,
geom = GeomCircle2,
position = position,
show.legend = show.legend,
inherit.aes = inherit.aes,
params = list(
n = n,
na.rm = na.rm,
...
)
)
}
#' @rdname geom_circle2
#' @format NULL
#' @usage NULL
#' @export
GeomCircle2 <- ggproto(
"GeomCircle2", GeomPolygon,
default_aes = aes(r0 = 1, colour = "grey35", fill = NA, size = 0.25, linetype = 1,
alpha = NA),
required_aes = c("x", "y"),
draw_panel = function(self, data, panel_params, coord, n = 60, linejoin = "mitre") {
aesthetics <- setdiff(names(data), c("x", "y", "group", "subgroup"))
dd <- point_to_circle(data$x, data$y, data$r0, n)
aes <- data[rep(1:nrow(data), each = n), aesthetics, drop = FALSE]
GeomPolygon$draw_panel(cbind(dd, aes), panel_params, coord)
},
draw_key = draw_key_circle
)
#' @noRd
point_to_circle <- function(x, y, r0, n = 60) {
nn <- length(x)
x <- rep(x, each = n)
y <- rep(y, each = n)
r0 <- 0.5 * sign(rep(r0, each = n)) * sqrt(abs(rep(r0, each = n)))
t <- rep(seq(0, 2*pi, length.out = n), nn)
new_data_frame(list(
x = r0 * cos(t) + x,
y = r0 * sin(t) + y,
group = rep(1:nn, each = n)
))
}
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