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@hadley
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#' Single line segments.
#'
#' @section Aesthetics:
#' \Sexpr[results=rd,stage=build]{ggplot2:::rd_aesthetics("geom", "segment")}
#'
#' @inheritParams geom_point
#' @param arrow specification for arrow heads, as created by arrow()
#' @param lineend Line end style (round, butt, square)
#' @seealso \code{\link{geom_path}} and \code{\link{geom_line}} for multi-
#' segment lines and paths.
#' @export
#' @examples
#' library(grid) # needed for arrow function
#' p <- ggplot(seals, aes(x = long, y = lat))
#' (p <- p + geom_segment(aes(xend = long + delta_long, yend = lat + delta_lat),
#' arrow = arrow(length = unit(0.1,"cm"))))
#'
#' if (require("maps")) {
#'
#' xlim <- range(seals$long)
#' ylim <- range(seals$lat)
#' usamap <- data.frame(map("world", xlim = xlim, ylim = ylim, plot =
#' FALSE)[c("x","y")])
#' usamap <- rbind(usamap, NA, data.frame(map('state', xlim = xlim, ylim
#' = ylim, plot = FALSE)[c("x","y")]))
#' names(usamap) <- c("long", "lat")
#'
#' p + geom_path(data = usamap) + scale_x_continuous(limits = xlim)
#' }
#'
#' # You can also use geom_segment to recreate plot(type = "h") :
#' counts <- as.data.frame(table(x = rpois(100,5)))
#' counts$x <- as.numeric(as.character(counts$x))
#' with(counts, plot(x, Freq, type = "h", lwd = 10))
#'
#' qplot(x, Freq, data = counts, geom = "segment",
#' yend = 0, xend = x, size = I(10))
#'
#' # Adding line segments
#' library(grid) # needed for arrow function
#' b <- ggplot(mtcars, aes(wt, mpg)) + geom_point()
#' b + geom_segment(aes(x = 2, y = 15, xend = 2, yend = 25))
#' b + geom_segment(aes(x = 2, y = 15, xend = 3, yend = 15))
#' b + geom_segment(aes(x = 5, y = 30, xend = 3.5, yend = 25),
#' arrow = arrow(length = unit(0.5, "cm")))
geom_segment <- function (mapping = NULL, data = NULL, stat = "identity",
position = "identity", arrow = NULL, lineend = "butt", na.rm = FALSE, ...) {
GeomSegment$new(mapping = mapping, data = data, stat = stat,
position = position, arrow = arrow, lineend = lineend, na.rm = na.rm, ...)
}
GeomSegment <- proto(Geom, {
objname <- "segment"
draw <- function(., data, scales, coordinates, arrow = NULL,
lineend = "butt", na.rm = FALSE, ...) {
data <- remove_missing(data, na.rm = na.rm,
c("x", "y", "xend", "yend", "linetype", "size", "shape"),
name = "geom_segment")
if (empty(data)) return(zeroGrob())
if (is.linear(coordinates)) {
return(with(coord_transform(coordinates, data, scales),
segmentsGrob(x, y, xend, yend, default.units="native",
gp = gpar(col=alpha(colour, alpha), fill = alpha(colour, alpha),
lwd=size * .pt, lty=linetype, lineend = lineend),
arrow = arrow)
))
}
data$group <- 1:nrow(data)
starts <- subset(data, select = c(-xend, -yend))
ends <- rename(subset(data, select = c(-x, -y)), c("xend" = "x", "yend" = "y"),
warn_missing = FALSE)
pieces <- rbind(starts, ends)
pieces <- pieces[order(pieces$group),]
GeomPath$draw_groups(pieces, scales, coordinates, arrow = arrow, ...)
}
default_stat <- function(.) StatIdentity
required_aes <- c("x", "y", "xend", "yend")
default_aes <- function(.) aes(colour="black", size=0.5, linetype=1, alpha = NA)
guide_geom <- function(.) "path"
})
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