grid.path {grid} R Documentation

## Draw a Path

### Description

These functions create and draw one or more paths. The final point of a path will automatically be connected to the initial point.

### Usage

pathGrob(x, y,
id=NULL, id.lengths=NULL,
pathId=NULL, pathId.lengths=NULL,
rule="winding",
default.units="npc",
name=NULL, gp=gpar(), vp=NULL)
grid.path(...)


### Arguments

 x A numeric vector or unit object specifying x-locations. y A numeric vector or unit object specifying y-locations. id A numeric vector used to separate locations in x and y into sub-paths. All locations with the same id belong to the same sub-path. id.lengths A numeric vector used to separate locations in x and y into sub-paths. Specifies consecutive blocks of locations which make up separate sub-paths. pathId A numeric vector used to separate locations in x and y into distinct paths. All locations with the same pathId belong to the same path. pathId.lengths A numeric vector used to separate locations in x and y into paths. Specifies consecutive blocks of locations which make up separate paths. rule A character value specifying the fill rule: either "winding" or "evenodd". default.units A string indicating the default units to use if x or y are only given as numeric vectors. name A character identifier. gp An object of class "gpar", typically the output from a call to the function gpar. This is basically a list of graphical parameter settings. vp A Grid viewport object (or NULL). ... Arguments passed to pathGrob().

### Details

Both functions create a path grob (a graphical object describing a path), but only grid.path draws the path (and then only if draw is TRUE).

A path is like a polygon except 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.

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

A grob object.

### Author(s)

Paul Murrell

Grid, viewport

### Examples

pathSample <- function(x, y, rule, gp = gpar()) {
if (is.na(rule))
grid.path(x, y, id = rep(1:2, each = 4), gp = gp)
else
grid.path(x, y, id = rep(1:2, each = 4), rule = rule, gp = gp)
if (!is.na(rule))
grid.text(paste("Rule:", rule), y = 0, just = "bottom")
}

pathTriplet <- function(x, y, title) {
pushViewport(viewport(height = 0.9, layout = grid.layout(1, 3),
gp = gpar(cex = .7)))
grid.rect(y = 1, height = unit(1, "char"), just = "top",
gp = gpar(col = NA, fill = "grey"))
grid.text(title, y = 1, just = "top")
pushViewport(viewport(layout.pos.col = 1))
pathSample(x, y, rule = "winding",
gp = gpar(fill = "grey"))
popViewport()
pushViewport(viewport(layout.pos.col = 2))
pathSample(x, y, rule = "evenodd",
gp = gpar(fill = "grey"))
popViewport()
pushViewport(viewport(layout.pos.col = 3))
pathSample(x, y, rule = NA)
popViewport()
popViewport()
}

pathTest <- function() {
grid.newpage()
pushViewport(viewport(layout = grid.layout(5, 1)))
pushViewport(viewport(layout.pos.row = 1))
pathTriplet(c(.1, .1, .9, .9, .2, .2, .8, .8),
c(.1, .9, .9, .1, .2, .8, .8, .2),
"Nested rectangles, both clockwise")
popViewport()
pushViewport(viewport(layout.pos.row = 2))
pathTriplet(c(.1, .1, .9, .9, .2, .8, .8, .2),
c(.1, .9, .9, .1, .2, .2, .8, .8),
"Nested rectangles, outer clockwise, inner anti-clockwise")
popViewport()
pushViewport(viewport(layout.pos.row = 3))
pathTriplet(c(.1, .1, .4, .4, .6, .9, .9, .6),
c(.1, .4, .4, .1, .6, .6, .9, .9),
"Disjoint rectangles")
popViewport()
pushViewport(viewport(layout.pos.row = 4))
pathTriplet(c(.1, .1, .6, .6, .4, .4, .9, .9),
c(.1, .6, .6, .1, .4, .9, .9, .4),
"Overlapping rectangles, both clockwise")
popViewport()
pushViewport(viewport(layout.pos.row = 5))
pathTriplet(c(.1, .1, .6, .6, .4, .9, .9, .4),
c(.1, .6, .6, .1, .4, .4, .9, .9),
"Overlapping rectangles, one clockwise, other anti-clockwise")
popViewport()
popViewport()
}

pathTest()

# Drawing multiple paths at once
holed_rect <- cbind(c(.15, .15, -.15, -.15, .1, .1, -.1, -.1),
c(.15, -.15, -.15, .15, .1, -.1, -.1, .1))
holed_rects <- rbind(
holed_rect + matrix(c(.7, .2), nrow = 8, ncol = 2, byrow = TRUE),
holed_rect + matrix(c(.7, .8), nrow = 8, ncol = 2, byrow = TRUE),
holed_rect + matrix(c(.2, .5), nrow = 8, ncol = 2, byrow = TRUE)
)
grid.newpage()
grid.path(x = holed_rects[, 1], y = holed_rects[, 2],
id = rep(1:6, each = 4), pathId = rep(1:3, each = 8),
gp = gpar(fill = c('red', 'blue', 'green')),
rule = 'evenodd')

# Not specifying pathId will treat all points as part of the same path, thus
# having same fill
grid.newpage()
grid.path(x = holed_rects[, 1], y = holed_rects[, 2],
id = rep(1:6, each = 4),
gp = gpar(fill = c('red', 'blue', 'green')),
rule = 'evenodd')


[Package grid version 4.2.0 Index]