polygon {base}

R Documentation

Polygon Drawing

Description

polygon draws the polygons whose vertices are given in x and y.

Usage

polygon(x, y = NULL, density = NULL, angle = 45,
        border = NULL, col = NA, lty = NULL, xpd = NULL, ...)

Arguments

x, y	vectors containing the coordinates of the vertices of the polygon.
density	the density of shading lines, in lines per inch. The default value of NULL means that no shading lines are drawn. Non-positive values of density also inhibit the drawing of shading lines.
angle	the slope of shading lines, given as an angle in degrees (counter-clockwise).
col	the color for filling the polygon. The default, NA, is to leave polygons unfilled.
border	the color to draw the border. The default, NULL, uses par("fg"). Use border=0 to omit borders.
lty	the line type to be used, as in par.
xpd	(where) should clipping take place? Defaults to par("xpd").
...	graphical parameters can be given as arguments to polygon.

Details

The coordinates can be passed in a plotting structure (a list with x and y components), a two-column matrix, .... See xy.coords.

It is assumed that the polygon is closed by joining the last point to the first point.

The coordinates can contain missing values. The behaviour is similar to that of lines, except that instead of breaking a line into several lines, NA values break the polygon into several complete polygons (including closing the last point to the first point). See the examples below.

When multiple polygons are produced, the values of density, angle, col, border, and lty are recycled in the usual manner.

Bugs

The present shading algorithm can produce incorrect results for self-intesecting polygons.

Author(s)

The code implementing polygon shading was donated by Kevin Buhr buhr@stat.wisc.edu.

See Also

segments for even more flexibility, lines, rect, box, abline.

Examples

x <- c(1:9,8:1)
y <- c(1,2*(5:3),2,-1,17,9,8,2:9)
op <- par(mfcol=c(3,1))
for(xpd in c(FALSE,TRUE,NA)) {
  plot(1:10, main=paste("xpd =", xpd)) ; box("figure", col = "pink", lwd=3)
  polygon(x,y, xpd=xpd, col = "orange", lty=2, lwd=2, border = "red")
}
par(op)

n <- 100
xx <- c(0:n, n:0)
yy <- c(c(0,cumsum(rnorm(n))), rev(c(0,cumsum(rnorm(n)))))
plot   (xx, yy, type="n", xlab="Time", ylab="Distance")
polygon(xx, yy, col="gray", border = "red")
title("Distance Between Brownian Motions")

# Multiple polygons from NA values
# and recycling of col, border, and lty
op <- par(mfrow=c(2,1))
plot(c(1,9), 1:2, type="n")
polygon(1:9, c(2,1,2,1,1,2,1,2,1),
        col=c("red", "blue"),
        border=c("green", "yellow"),
        lwd=3, lty=c("dashed", "solid"))
plot(c(1,9), 1:2, type="n")
polygon(1:9, c(2,1,2,1,NA,2,1,2,1),
        col=c("red", "blue"),
        border=c("green", "yellow"),
        lwd=3, lty=c("dashed", "solid"))
par(op)

# Line-shaded polygons
plot(c(1,9), 1:2, type="n")
polygon(1:9, c(2,1,2,1,NA,2,1,2,1),
        density=c(10, 20), angle=c(-45, 45))

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