| Grid Viewports {grid} | R Documentation |
These functions create viewports, which describe rectangular regions on a graphics device and define a number of coordinate systems within those regions.
viewport(x = unit(0.5, "npc"), y = unit(0.5, "npc"),
width = unit(1, "npc"), height = unit(1, "npc"),
default.units = "npc", just = "centre",
gp = gpar(), clip = "inherit",
xscale = c(0, 1), yscale = c(0, 1),
angle = 0,
layout = NULL,
layout.pos.row = NULL, layout.pos.col = NULL,
name = NULL)
vpList(...)
vpStack(...)
vpTree(parent, children)
x |
A numeric vector or unit object specifying x-location. |
y |
A numeric vector or unit object specifying y-location. |
width |
A numeric vector or unit object specifying width. |
height |
A numeric vector or unit object specifying height. |
default.units |
A string indicating the default units to use
if x, y, width, or height
are only given as numeric vectors. |
just |
A string or numeric
vector specifying the justification of the viewport
relative to its (x, y) location. If there are two values, the first
value specifes horizontal justification and the second value specifies
vertical justification. Possible string values are: "left",
"right", "centre", "center", "bottom",
and "top". For numeric values, 0 means left alignment
and 1 means right alignment.
|
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. |
clip |
One of "on", "inherit", or
"off", indicating whether to
clip to the extent of this viewport, inherit the clipping region
from the parent viewport, or turn clipping off altogether.
For back-compatibility, a logical value of TRUE corresponds
to "on" and FALSE corresponds to "inherit". |
xscale |
A numeric vector of length two indicating the minimum and maximum on the x-scale. |
yscale |
A numeric vector of length two indicating the minimum and maximum on the y-scale. |
angle |
A numeric value indicating the angle of rotation of the viewport. Positive values indicate the amount of rotation, in degrees, anitclockwise from the positive x-axis. |
layout |
A Grid layout object which splits the viewport into subregions. |
layout.pos.row |
A numeric vector giving the rows occupied by this viewport in its parent's layout. |
layout.pos.col |
A numeric vector giving the columns occupied by this viewport in its parent's layout. |
name |
A character value to uniquely identify the viewport once it has been pushed onto the viewport tree. |
... |
Any number of grid viewport objects. |
parent |
A grid viewport object. |
children |
A vpList object. |
The location and size of a viewport are relative to the coordinate
systems defined by the viewport's parent (either a graphical device
or another viewport). The location and size can be specified in a
very flexible way by specifying them with unit objects.
When specifying the location of a viewport, specifying
both layout.pos.row and layout.pos.col as NULL
indicates that
the viewport ignores its parent's layout and specifies its own
location and size (via its locn). If only one of
layout.pos.row and layout.pos.col is NULL, this
means occupy ALL of the appropriate row(s)/column(s). For example,
layout.pos.row = 1 and layout.pos.col = NULL means
occupy all of row 1. Specifying non-NULL values for both
layout.pos.row and layout.pos.col means occupy the
intersection of the appropriate rows and columns. If a vector of
length two is
specified for layout.pos.row or layout.pos.col, this
indicates a range of rows or columns to occupy. For example,
layout.pos.row = c(1, 3) and layout.pos.col = c(2, 4)
means occupy cells in the intersection of rows 1, 2, and 3, and
columns, 2, 3, and 4.
Clipping obeys only the most recent viewport clip setting. For example, if you clip to viewport1, then clip to viewport2, the clipping region is determined wholly by viewport2, the size and shape of viewport1 is irrelevant (until viewport2 is popped of course).
If a viewport is rotated (because of its own angle setting
or because it is within another viewport which is rotated) then
the clip flag is ignored.
Viewport names need not be unique. When pushed, viewports
sharing the same parent must have unique names, which means that
if you push a viewport with the same name as an existing viewport,
the existing viewport will be replaced in the viewport tree.
A viewport name can be any string, but
grid uses the
reserved name "ROOT" for the top-level viewport. Also,
when specifying a viewport name in downViewport
and seekViewport, it is possible to provide a viewport
path, which consists of several names concatenated using the
separator (currently ::). Consequently, it is not
advisable to use this separator in viewport names.
The viewports in a vpList are pushed in parallel. The
viewports in a vpStack are pushed in series. When a
vpTree is pushed, the parent is pushed first, then the
children are pushed in parallel.
An R object of class viewport.
Paul Murrell
Grid,
pushViewport,
popViewport,
downViewport,
seekViewport,
upViewport,
unit,
grid.layout,
grid.show.layout.
# Diagram of a sample viewport
grid.show.viewport(viewport(x=0.6, y=0.6,
w=unit(1, "inches"), h=unit(1, "inches")))
# Demonstrate viewport clipping
clip.demo <- function(i, j, clip1, clip2) {
pushViewport(viewport(layout.pos.col=i,
layout.pos.row=j))
pushViewport(viewport(width=0.6, height=0.6, clip=clip1))
grid.rect(gp=gpar(fill="white"))
grid.circle(r=0.55, gp=gpar(col="red", fill="pink"))
popViewport()
pushViewport(viewport(width=0.6, height=0.6, clip=clip2))
grid.polygon(x=c(0.5, 1.1, 0.6, 1.1, 0.5, -0.1, 0.4, -0.1),
y=c(0.6, 1.1, 0.5, -0.1, 0.4, -0.1, 0.5, 1.1),
gp=gpar(col="blue", fill="light blue"))
popViewport(2)
}
grid.newpage()
grid.rect(gp=gpar(fill="grey"))
pushViewport(viewport(layout=grid.layout(2, 2)))
clip.demo(1, 1, FALSE, FALSE)
clip.demo(1, 2, TRUE, FALSE)
clip.demo(2, 1, FALSE, TRUE)
clip.demo(2, 2, TRUE, TRUE)
popViewport()
# Demonstrate turning clipping off
grid.newpage()
pushViewport(viewport(w=.5, h=.5, clip="on"))
grid.rect()
grid.circle(r=.6, gp=gpar(lwd=10))
pushViewport(viewport(clip="inherit"))
grid.circle(r=.6, gp=gpar(lwd=5, col="grey"))
pushViewport(viewport(clip="off"))
grid.circle(r=.6)
popViewport(3)
# Demonstrate vpList, vpStack, and vpTree
grid.newpage()
tree <- vpTree(viewport(w=0.8, h=0.8, name="A"),
vpList(vpStack(viewport(x=0.1, y=0.1, w=0.5, h=0.5,
just=c("left", "bottom"), name="B"),
viewport(x=0.1, y=0.1, w=0.5, h=0.5,
just=c("left", "bottom"), name="C"),
viewport(x=0.1, y=0.1, w=0.5, h=0.5,
just=c("left", "bottom"), name="D")),
viewport(x=0.5, w=0.4, h=0.9,
just="left", name="E")))
pushViewport(tree)
for (i in LETTERS[1:5]) {
seekViewport(i)
grid.rect()
grid.text(current.vpTree(FALSE),
x=unit(1, "mm"), y=unit(1, "npc") - unit(1, "mm"),
just=c("left", "top"),
gp=gpar(fontsize=8))
}