polygon               package: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))

