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#' Hexagonal heatmap of 2d bin counts
#'
#' Divides the plane into regular hexagons, counts the number of cases in
#' each hexagon, and then (by default) maps the number of cases to the hexagon
#' fill. Hexagon bins avoid the visual artefacts sometimes generated by
#' the very regular alignment of [geom_bin2d()].
#'
#' @eval rd_aesthetics("geom", "hex")
#' @seealso [stat_bin2d()] for rectangular binning
#' @param geom,stat Override the default connection between `geom_hex` and
#' `stat_binhex.`
#' @export
#' @inheritParams layer
#' @inheritParams geom_point
#' @export
#' @examples
#' d <- ggplot(diamonds, aes(carat, price))
#' d + geom_hex()
#'
#' \donttest{
#' # You can control the size of the bins by specifying the number of
#' # bins in each direction:
#' d + geom_hex(bins = 10)
#' d + geom_hex(bins = 30)
#'
#' # Or by specifying the width of the bins
#' d + geom_hex(binwidth = c(1, 1000))
#' d + geom_hex(binwidth = c(.1, 500))
#' }
geom_hex <- function(mapping = NULL, data = NULL,
stat = "binhex", position = "identity",
...,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE) {
layer(
data = data,
mapping = mapping,
stat = stat,
geom = GeomHex,
position = position,
show.legend = show.legend,
inherit.aes = inherit.aes,
params = list(
na.rm = na.rm,
...
)
)
}
#' @rdname ggplot2-ggproto
#' @format NULL
#' @usage NULL
#' @export
GeomHex <- ggproto("GeomHex", Geom,
draw_group = function(data, panel_params, coord) {
if (!inherits(coord, "CoordCartesian")) {
stop("geom_hex() only works with Cartesian coordinates", call. = FALSE)
}
coord <- coord$transform(data, panel_params)
ggname("geom_hex", hexGrob(
coord$x, coord$y, colour = coord$colour,
fill = alpha(coord$fill, coord$alpha)
))
},
required_aes = c("x", "y"),
default_aes = aes(colour = NA, fill = "grey50", size = 0.5, alpha = NA),
draw_key = draw_key_polygon
)
# Draw hexagon grob
# Modified from code by Nicholas Lewin-Koh and Martin Maechler
#
# @param x positions of hex centres
# @param y positions
# @param vector of hex sizes
# @param border colour
# @param fill colour
# @keyword internal
hexGrob <- function(x, y, size = rep(1, length(x)), colour = "grey50", fill = "grey90") {
stopifnot(length(y) == length(x))
dx <- resolution(x, FALSE)
dy <- resolution(y, FALSE) / sqrt(3) / 2 * 1.15
hexC <- hexbin::hexcoords(dx, dy, n = 1)
n <- length(x)
polygonGrob(
x = rep.int(hexC$x, n) * rep(size, each = 6) + rep(x, each = 6),
y = rep.int(hexC$y, n) * rep(size, each = 6) + rep(y, each = 6),
default.units = "native",
id.lengths = rep(6, n), gp = gpar(col = colour, fill = fill)
)
}