polypath {graphics}

Path Drawing

Description

path draws a path whose vertices are given in x and y.

Usage

polypath(x, y = NULL,
         border = NULL, col = NA, lty = par("lty"),
         rule = "winding", ...)

Arguments

x, y

vectors containing the coordinates of the vertices of the path.

col

the color for filling the path. The default, NA, is to leave paths unfilled.

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.

rule

character value specifying the path fill mode: either "winding" or "evenodd".

...

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 path 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 polygon, except that instead of breaking a polygon into several polygons, NA values break the path into several sub-paths (including closing the last point to the first point in each sub-path). See the examples below.

The distinction between a path and a polygon is that the former can contain holes, as interpreted by the fill rule; these fill a region if the path border encircles it an odd or non-zero number of times, respectively.

Hatched shading (as implemented for polygon()) is not (currently) supported.

Not all graphics devices support this function: for example xfig and pictex do not.

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, polygon.

par for how to specify colors.

Examples

plotPath <- function(x, y, col = "grey", rule = "winding") {
    plot.new()
    plot.window(range(x, na.rm = TRUE), range(y, na.rm = TRUE))
    polypath(x, y, col = col, rule = rule)
    if (!is.na(col))
        mtext(paste("Rule:", rule), side = 1, line = 0)
}

plotRules <- function(x, y, title) {
    plotPath(x, y)
    plotPath(x, y, rule = "evenodd")
    mtext(title, side = 3, line = 0)
    plotPath(x, y, col = NA)
}

op <- par(mfrow = c(5, 3), mar = c(2, 1, 1, 1))

plotRules(c(.1, .1, .9, .9, NA, .2, .2, .8, .8),
          c(.1, .9, .9, .1, NA, .2, .8, .8, .2),
          "Nested rectangles, both clockwise")
plotRules(c(.1, .1, .9, .9, NA, .2, .8, .8, .2),
          c(.1, .9, .9, .1, NA, .2, .2, .8, .8),
          "Nested rectangles, outer clockwise, inner anti-clockwise")
plotRules(c(.1, .1, .4, .4, NA, .6, .9, .9, .6),
          c(.1, .4, .4, .1, NA, .6, .6, .9, .9),
          "Disjoint rectangles")
plotRules(c(.1, .1, .6, .6, NA, .4, .4, .9, .9),
          c(.1, .6, .6, .1, NA, .4, .9, .9, .4),
          "Overlapping rectangles, both clockwise")
plotRules(c(.1, .1, .6, .6, NA, .4, .9, .9, .4),
          c(.1, .6, .6, .1, NA, .4, .4, .9, .9),
          "Overlapping rectangles, one clockwise, other anti-clockwise")

par(op)