#' Shade Geom
#'
#' @param sign scalar numeric value. If less than 0, add shade on cells with
#' negtive \code{r} values. If larger than 0, add shade on cells with positive
#' \code{r} values. If equals 0, add shade on cells except where \code{r} values
#' equals 0.
#' @inheritParams ggplot2::layer
#' @inheritParams ggplot2::geom_segment
#' @section Aesthetics:
#' \code{geom_shade()} understands the following aesthetics (required
#' aesthetics are in bold):
#' \itemize{
#' \item \strong{\code{x}}
#' \item \strong{\code{y}}
#' \item \strong{\code{r0}}
#' \item \code{alpha}
#' \item \code{colour}
#' \item \code{linetype}
#' \item \code{size}
#' }
#' @rdname geom_shade
#' @importFrom ggplot2 layer ggproto GeomSegment aes draw_key_blank
#' @importFrom grid grobTree
#' @author Houyun Huang, Lei Zhou, Jian Chen, Taiyun Wei
#' @export
geom_shade <- function(mapping = NULL, data = NULL,
stat = "identity", position = "identity",
...,
sign = 1,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE) {
layer(
data = data,
mapping = mapping,
stat = stat,
geom = GeomShade,
position = position,
show.legend = show.legend,
inherit.aes = inherit.aes,
params = list(
sign = sign,
na.rm = na.rm,
...
)
)
}
#' @rdname geom_shade
#' @format NULL
#' @usage NULL
#' @export
GeomShade <- ggproto(
"GeomShade", GeomSegment,
default_aes = aes(colour = "white", size = 0.25, linetype = 1, alpha = NA),
required_aes = c("x", "y", "r0"),
draw_panel = function(self, data, panel_params, coord, linejoin = "mitre",
sign = 1) {
aesthetics <- setdiff(names(data), c("x", "y", "r0"))
polys <- lapply(split(data, seq_len(nrow(data))), function(row) {
if(sign < 0) {
if(row$r0 >= 0) return(grid::nullGrob())
shade <- point_to_shade(row$x, row$y, row$r0)
aes <- new_data_frame(row[aesthetics])[rep(1, 3), ]
return(GeomSegment$draw_panel(cbind(shade, aes), panel_params, coord))
}
if(sign > 0) {
if(row$r0 <= 0) return(grid::nullGrob())
shade <- point_to_shade(row$x, row$y, row$r0)
aes <- new_data_frame(row[aesthetics])[rep(1, 3), ]
return(GeomSegment$draw_panel(cbind(shade, aes), panel_params, coord))
}
if(sign == 0) {
if(row$r0 == 0) return(grid::nullGrob())
shade <- point_to_shade(row$x, row$y, row$r0)
aes <- new_data_frame(row[aesthetics])[rep(1, 3), ]
return(GeomSegment$draw_panel(cbind(shade, aes), panel_params, coord))
}
})
ggplot2:::ggname("geom_shade", do.call("grobTree", polys))
},
draw_key = draw_key_blank
)
#' @noRd
point_to_shade <- function(x, y, sign)
{
if(sign > 0) {
xx <- c(x - 0.5, x - 0.5, x)
xend <- c(x, x + 0.5, x + 0.5)
yy <- c(y, y + 0.5, y + 0.5)
yend <- c(y - 0.5, y - 0.5, y)
}
if(sign < 0) {
xx <- c(x, x - 0.5, x - 0.5)
xend <- c(x + 0.5, x + 0.5, x)
yy <- c(y - 0.5, y - 0.5, y)
yend <- c(y, y + 0.5, y + 0.5)
}
new_data_frame(list(
x = xx,
y = yy,
xend = xend,
yend = yend
))
}
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