polygon
Polygon Drawing
polygon draws the polygons whose vertices are
given in x and y.
- Keywords
- aplot
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
NULLmeans that no shading lines are drawn. A zero value ofdensitymeans no shading nor filling whereas negative values andNAsuppress 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, unlessdensityis specified. (For back-compatibility,NULLis equivalent toNA.) Ifdensityis 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 usepar("fg"). Useborder = NAto omit borders.For compatibility with S,
bordercan also be logical, in which caseFALSEis equivalent toNA(borders omitted) andTRUEis equivalent toNULL(use the foreground colour),- lty
the line type to be used, as in
par.- …
graphical parameters such as
xpd,lend,ljoinandlmitrecan 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.
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
library(graphics)
# NOT RUN {
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))
# }