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polygon: Polygon Drawing

polygon

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"),
        ..., fillOddEven = FALSE)

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.
`fillOddEven`	logical controlling the polygon shading mode: see below for details. Default `FALSE`.

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.

Shading of polygons is only implemented for linear plots: if either axis is on log scale then shading is omitted, with a warning.

Bugs

Self-intersecting polygons may be filled using either the “odd-even” or “non-zero” rule. These fill a region if the polygon border encircles it an odd or non-zero number of times, respectively. Shading lines are handled internally by R according to the fillOddEven argument, but device-based solid fills depend on the graphics device. The windows, pdf and postscript devices have their own fillOddEven argument to control this.

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.

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))