#' Star glyphs
#'
#' geom_star draws the type of glyph commonly called a star plot, radar plot,
#' or polar plot.
#'
#' @param mapping The aesthetic mapping, usually constructed with
#' \code{\link[ggplot2]{aes}}. Only needs to be set at the layer level if you
#' are overriding the plot defaults. x and y will determine where the center
#' of the star should appear. r and angle will determine the polar coordinate
#' system for the star.
#' @param data A layer specific dataset - only needed if you want to override
#' the plot defaults
#' @param stat The statistical transformation to use for this layer.
#' @param position The position adjustment to use for overlapping points in this
#' layer
#' @param na.rm If FALSE (the default), removes missing values with a warning.
#' If TRUE, silently removes missing variables.
#' @param r.zero logical. Should the origin of the star correspond to r = 0? If
#' FALSE, origin corresponds to lowest value of r.
#' @param ... other arguments passed on to \code{\link[ggplot2]{layer}}. This
#' can include aesthetics whose values you want to set, not map. See
#' \code{\link[ggplot2]{layer}} for more details.
#'
#' @section Aesthetics:
#' \code{geom_star} understands the following aesthetics: x, y, colour, fill,
#' size, linetype, weight, and alpha.
#'
#' @examples
#' library(ggplot2)
#' ggplot(nasa) +
#' # borders("state") +
#' geom_subplot(aes(long, lat, group = id, subplot =
#' geom_star(
#' aes(x = 0, y = 0, r = surftemp, angle = date, fill = mean(surftemp)),
#' r.zero = FALSE
#' ))
#' ) +
#' coord_quickmap()
#' @export
geom_star <- function(mapping = NULL, data = NULL, stat = "identity",
position = "identity", na.rm = FALSE, r.zero = TRUE, ...) {
GeomStar$new(mapping = mapping, data = data, stat = stat,
position = position, r.zero = r.zero, ...)
}
GeomStar <- proto::proto(ggplot2:::Geom, {
objname <- "star"
# turn cartesian coordinates polar
reparameterise <- function(., df, params) {
# scale x to be between 0 and 2*pi
df$theta <- unlist(rescale_2pi(df["angle"]))
df$r <- unlist(rescale_01(df["r"], zero = params$r.zero))
include_origin <- function(data) {
data <- data[order(data$theta, data$r), ]
if (data$theta[1] > 0.01) {
first <- data[1, ]
first$theta <- 0
first$r <- 0
data <- rbind(first, data)
}
if (data$theta[length(data$theta)] < 6.27) {
last <- data[length(data$theta), ]
last$theta <- 6.28
last$r <- 0
data <- rbind(data, last)
}
# for centering
origin <- data[1, ]
origin$r <- 0
origin$theta <- 0
origin$plot <- FALSE
data$plot <- TRUE
# remove missing points from plot
# (otherwise each star will becaome separate polygons)
data$plot[is.na(data$r) | is.na(data$angle)] <- FALSE
rbind(data, origin)
}
df <- ddply(df, c("group", "PANEL"), include_origin)
df$x <- df$r * cos(df$theta)
df$y <- df$r * sin(df$theta)
# ensure that (0,0) is plotted in center of graph
center <- function(data) {
origin <- data[data$r == 0 & data$theta == 0, ][1, ]
xtreme <- max(abs(data$x - origin$x))
ytreme <- max(abs(data$y - origin$y))
fullspan <- data[c(1,1,1,1), ]
fullspan$x <- c(origin$x - xtreme, origin$x - xtreme,
origin$x + xtreme, origin$x + xtreme)
fullspan$y <- c(origin$y - ytreme, origin$y + ytreme,
origin$y - ytreme, origin$y + ytreme)
fullspan$plot <- FALSE
rbind(data, fullspan)
}
ddply(df, c("group", "PANEL"), center)
}
draw <- function(., data, scales, coordinates, ...) {
data <- data[data$plot, ]
data <- data[order(data$theta, data$r), ]
ggname(.$my_name(),
gTree(children = gList(
with(coord_munch(coordinates, data, scales),
polygonGrob(x, y, default.units = "native",
gp = gpar(col = colour, fill = alpha(fill, alpha),
lwd = size * .pt, lty = linetype)
)
)
))
)
}
default_stat <- function(.) StatIdentity
default_aes <- function(.) {
aes(weight = 1, colour = "grey20", fill = "NA", alpha = NA,
linetype = "solid", size = 0.5, r.zero = TRUE)
}
required_aes <- c("x", "y")
guide_geom <- function(.) "polygon"
draw_legend <- function(., data, ...) {
data <- aesdefaults(data, .$default_aes(), list(...))
with(data, grobTree(
rectGrob(gp = gpar(col = colour, fill = alpha(fill, alpha),
lty = linetype)),
linesGrob(gp = gpar(col = colour, lwd = size * .pt,
lineend="butt", lty = linetype))
))
}
new <- function(., mapping = NULL, data = NULL, stat = NULL,
position = NULL, na.rm = FALSE, ...) {
# compute_aesthetics should retunr numeric x and y scales
# to allow smooth use of the output of reparameterise
if (!("angle" %in% names(mapping))) {
if ("x" %in% names(mapping)) {
names(mapping)[names(mapping) == "x"] <- "angle"
mapping$x <- 0
} else {
stop("Missing required aesthetic for geom_star: angle", call. = F)
}
} else {
if (!("x" %in% names(mapping))) {
mapping$x <- 0
}
}
if (!("r" %in% names(mapping))) {
if ("y" %in% names(mapping)) {
names(mapping)[names(mapping) == "y"] <- "r"
mapping$y <- 0
} else {
stop(cat("Missing required aesthetic for geom_star: r\n",
"do you want geom_freqstar?"), call. = F)
}
} else {
if (!("y" %in% names(mapping))) {
mapping$y <- 0
}
}
do.call("layer", list(mapping = mapping, data = data, stat = stat,
geom = ., position = position, na.rm = na.rm, ...))
}
})
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