grid.layout: Create a Grid Layout

Description

This function returns a Grid layout, which describes a subdivision of a rectangular region.

Usage

grid.layout(nrow = 1, ncol = 1,
        widths = unit(rep_len(1, ncol), "null"),
        heights = unit(rep_len(1, nrow), "null"),
        default.units = "null", respect = FALSE,
        just="centre")

Arguments

nrow

An integer describing the number of rows in the layout.

ncol

An integer describing the number of columns in the layout.

widths

A numeric vector or unit object describing the widths of the columns in the layout.

heights

A numeric vector or unit object describing the heights of the rows in the layout.

default.units

A string indicating the default units to use if widths or heights are only given as numeric vectors.

respect

A logical value or a numeric matrix. If a logical, this indicates whether row heights and column widths should respect each other. If a matrix, non-zero values indicate that the corresponding row and column should be respected (see examples below).

just

A string or numeric vector specifying how the layout should be justified if it is not the same size as its parent viewport. If there are two values, the first value specifies 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. NOTE that in this context, "left", for example, means align the left edge of the left-most layout column with the left edge of the parent viewport.

Value

A Grid layout object.

WARNING

This function must NOT be confused with the base R graphics function layout. In particular, do not use layout in combination with Grid graphics. The documentation for layout may provide some useful information and this function should behave identically in comparable situations. The grid.layout function has added the ability to specify a broader range of units for row heights and column widths, and allows for nested layouts (see viewport).

Details

The unit objects given for the widths and heights of a layout may use a special units that only has meaning for layouts. This is the "null" unit, which indicates what relative fraction of the available width/height the column/row occupies. See the reference for a better description of relative widths and heights in layouts.

References

Murrell, P. R. (1999). Layouts: A Mechanism for Arranging Plots on a Page. Journal of Computational and Graphical Statistics, 8, 121--134. 10.2307/1390924.

Examples

# NOT RUN {
## A variety of layouts (some a bit mid-bending ...)
layout.torture()
## Demonstration of layout justification
grid.newpage()
testlay <- function(just="centre") {
  pushViewport(viewport(layout=grid.layout(1, 1, widths=unit(1, "inches"),
                          heights=unit(0.25, "npc"),
                          just=just)))
  pushViewport(viewport(layout.pos.col=1, layout.pos.row=1))
  grid.rect()
  grid.text(paste(just, collapse="-"))
  popViewport(2)
}
testlay()
testlay(c("left", "top"))
testlay(c("right", "top"))
testlay(c("right", "bottom"))
testlay(c("left", "bottom"))
testlay(c("left"))
testlay(c("right"))
testlay(c("bottom"))
testlay(c("top"))
# }