polygon {graphics}

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 = par("lty"), ...)

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. A zero value of density means no shading nor filling whereas negative values (and NA) suppress shading (and so allow color filling).
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, unless density is specified. (For back-compatibility, NULL is equivalent to NA.) If density is specified with a positive value this gives the color of the shading lines.
border	the color to draw the border. The default, NULL, means to use par("fg"). Use border = NA to omit borders. For compatibility with S, border can also be logical, in which case FALSE is equivalent to NA (borders omitted) and TRUE is equivalent to NULL (use the foreground colour),
lty	the line type to be used, as in par.
...	graphical parameters such as xpd, lend, ljoin and lmitre can be given as arguments.

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 to be 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-intersecting polygons.

Author(s)

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

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Murrell, P. (2005) R Graphics. Chapman & Hall/CRC Press.

See Also

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

par for how to specify colors.

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(stats::rnorm(n))), rev(c(0,cumsum(stats::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))

---