R: Produce a Legend or Key (Grid Function)

draw.leg {IDPmisc}

R Documentation

Produce a Legend or Key (Grid Function)

Description

Produces (and possibly draws) a Grid frame grob which is a legend that can be placed in other Grid plots. draw.leg is a slightly enhanced version of draw.key in package lattice V 0.12-3.

Usage

draw.leg(key, draw=FALSE, vp=NULL)

Arguments

`key`	A list determining the key. See details below and the documentation for `xyplot`.
`draw`	logical, whether the grob is to be drawn.
`vp`	viewport

Details

Three new components are added to the list key of the original code in package lattice V 0.12-3: between.rows, between.title, adj.title. They allow to format the legend in a more flexible way. To ease the use of draw.leg, the full description of draw.key and the here interesting part of xyplot are also included:
The key essentially consists of a number of columns, possibly divided into blocks, each containing some rows. The contents of the key are determined by (possibly repeated) components named “rectangles”, “lines”, “points” or “text”. Each of these must be lists with relevant graphical parameters (see later) controlling their appearance. The key list itself can contain graphical parameters, these would be used if relevant graphical components are omitted from the other components.

The length (number of rows) of each such column (except “text”s) is taken to be the largest of the lengths of the graphical components, including the ones specified outside (see the entry for rep below for details on this). The “text” component has to have a character or expression vector as its first component, and the length of this vector determines the number of rows.

The graphical components that can be included in key (and also in the components named “text”, “lines”, “points” and “rectangles” as appropriate) are:

cex=1
col="black"
lty=1
lwd=1
font=1
fontface
fontfamily
pch=8
adj=0
type="l"
size=5
angle=0
density=-1

adj, angle and density are currently unimplemented. size determines the width of columns of rectangles and lines in character widths. type is relevant for lines; "l" denotes a line, "p" denotes a point, and "b" and "o" both denote both together.

Other possible components of key are:

between: numeric vector giving the amount of space (character widths) surrounding each column (split equally on both sides),
title: string or expression giving a title for the key
rep: logical, defaults to TRUE. By default, it's assumed that all columns in the key (except the “text”s) will have the same number of rows, and all components are replicated to be as long as the longest. This can be suppressed by specifying rep=FALSE, in which case the length of each column will be determined by components of that column alone.
cex.title: cex for the title
background: background color, defaults to default background
border: either a color for the border, or a logical. In the latter case, the border color is black if border is TRUE, and no border is drawn if it is FALSE (the default)
transparent=FALSE: logical, whether key area should have a transparent background
columns: the number of columns column-blocks the key is to be divided into, which are drawn side by side.
between.columns: Space between column blocks, in addition to between.
between.rows: New argument: Space between rows.
between.title: New argument: Space between top row and title of legend.
adj.title: New argument: Adjustment of title in respect to body of legend.
adj.title = 0 adjusts the title to the left,
adj.title = 1 adjusts the title to the right and
adj.title = 0.5 (=default) centers the title.
divide: Number of point symbols to divide each line when type is "b" or "o" in lines.

Value

A Grid frame object (that inherits from “grob”)

Author(s)

Deepayan Sarkar, modified by Rene Locher

Examples

require(grid)

## Legend 2 cm below and 1 cm left of the upper right corner
grid.newpage()
key <- draw.leg(key =
                    list(rectangles = list(col=1:3,
                             size = 2,
                             lwd = 0.5),
                         text = list(LETTERS[1:3]),
                         cex = 1.2,
                         between = 2,
                         between.rows = 0.5,
                         between.title = 0.7,
                         title = "component",
                         cex.title = 1.4,
                         transparent = TRUE))

vp.key <-  viewport(x = convertX(unit(1,"npc")-unit(1,"cm"),"cm"),
                    y = convertY(unit(1,"npc")-unit(2,"cm"),"cm"),
                    width=grobWidth(key),
                    height=grobHeight(key),
                    just=c("right","top"))

pushViewport(vp.key)
grid.draw(key)
popViewport()

##----------------------------------------
## Legend 1 cm above the lower left corner
key <- draw.leg(key = list(rectangles = list(col=1:3,
                             size = 4,
                             lwd = 0.5),
                  text=list(letters[1:3]),
                  lines=list(col=1:3),
                  cex=2,
                  between=2,
                  between.rows=0.5,
                  between.title=0.7,
                  title = "component",
                  adj.title = 0,
                  cex.title = 2.4,
                  transparent = TRUE))

vp.key <-  viewport(x = 0,
                    y = unit(1,"cm"),
                    width=grobWidth(key),
                    height=grobHeight(key),
                    just=c("left","bottom"))

grid.newpage()
pushViewport(vp.key)
grid.draw(key)
popViewport()

[Package IDPmisc version 1.1.21 Index]