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# center and radius are x, y, radius
# specify either angle1 and angle2 in radians or deg1 and deg2 in degrees
# n is number of pieces arc is divided into for the approximation
# ... is passed to segments
# e.g.
# plot(1:10)
# draw.arc(5, 6, deg1 = 45, deg2 = 90, col = "red")
#
draw.arc <- function(x = 1, y = NULL, radius = 1,
angle1 = deg1 * pi / 180, angle2 = deg2 * pi / 180,
deg1 = 0, deg2 = 45, n = 35, col = 1, ...) {
draw.arc.0 <- function(x, y, radius, angle1, angle2, n, col = col, ...) {
xylim<-par("usr")
plotdim<-par("pin")
ymult<-(xylim[4]-xylim[3])/(xylim[2]-xylim[1])*plotdim[1]/plotdim[2]
angle <- angle1 + seq(0, length = n) * (angle2 - angle1) / n
p1x <- x + radius * cos(angle)
p1y <- y + radius * sin(angle) * ymult
angle <- angle1 + seq(length = n) * (angle2 - angle1) / n
p2x <- x + radius * cos(angle)
p2y <- y + radius * sin(angle) * ymult
segments(p1x, p1y, p2x, p2y, col = col, ...)
}
xy <- xy.coords(x, y); x <- xy$x; y <- xy$y
a1 <- pmin(angle1, angle2); a2 <- pmax(angle1, angle2)
angle1 <- a1; angle2 <- a2
args <-
data.frame(x,y,radius,angle1,angle2,n,col,stringsAsFactors=FALSE)
for(i in 1:nrow(args)) do.call("draw.arc.0", c(args[i, ], ...))
invisible(args)
}
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