Add Legends to Plots

Description

This function can be used to add legends to plots. Note that a call to the function locator(1) can be used in place of the x and y arguments.

Usage

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legend(x, y = NULL, legend, fill = NULL, col = par("col"),
  border = "black", lty, lwd, pch, angle = 45, density = NULL,
  bty = "o", bg = par("bg"), box.lwd = par("lwd"), box.lty = par("lty"),
  box.col = par("fg"), pt.bg = NA, cex = 1, pt.cex = cex,
  pt.lwd = lwd, xjust = 0, yjust = 1, x.intersp = 1, y.intersp = 1,
  adj = c(0, 0.5), text.width = NULL, text.col = par("col"),
  merge = do.lines && has.pch, trace = FALSE, plot = TRUE, ncol = 1,
  horiz = FALSE, title = NULL, inset = 0, xpd, title.col = text.col,
  title.adj = 0.5, seg.len = 2)

Arguments

x

the x coordinates to be used to position the legend.

y

the y coordinates to be used to position the legend. x and y can be specified by keyword or in any way which is accepted by xy.coords: See ‘Details’.

legend

a character or expression vector. of length >= 1 to appear in the legend. Other objects will be coerced by as.graphicsAnnot.

fill

if specified, this argument will cause boxes filled with the specified colors (or shaded in the specified colors) to appear beside the legend text.

col

the color of points or lines appearing in the legend.

border

the border color for the boxes (used only if fill is specified).

lty

the line types for lines appearing in the legend.

lwd

the line widths for lines appearing in the legend. One of lty and lwd must be specified for line drawing.

pch

the plotting symbols appearing in the legend, either as vector of 1-character strings, or one (multi character) string. Must be specified for symbol drawing.

angle

angle of shading lines.

density

the density of shading lines, if numeric and positive. If NULL or negative or NA color filling is assumed.

bty

the type of box to be drawn around the legend. The allowed values are "o" (the default) and "n".

bg

the background color for the legend box. (Note that this is only used if bty != "n".)

box.lwd

the line type for the legend box.

box.lty

the line width for the legend box.

box.col

the color for the legend box.

pt.bg

the background color for the points, corresponding to its argument bg.

cex

character expansion factor relative to current par("cex").

pt.cex

expansion factor(s) for the points.

pt.lwd

line width for the points, defaults to the one for lines, or if that is not set, to par("lwd").

xjust

how the legend is to be justified relative to the legend x location. A value of 0 means left justified, 0.5 means centered and 1 means right justified.

yjust

the same as xjust for the legend y location.

x.intersp

character interspacing factor for horizontal (x) spacing.

y.intersp

the same for vertical (y) line distances.

adj

numeric of length 1 or 2; the string adjustment for legend text. Useful for y-adjustment when labels are plotmath expressions.

text.width

the width of the legend text in x ("user") coordinates. (Should be positive even for a reversed x axis.) Defaults to the proper value computed by strwidth(legend).

text.col

the color used for the legend text.

merge

logical; if TRUE, merge points and lines but not filled boxes. Defaults to TRUE if there are points and lines.

trace

logical; if TRUE, shows how legend does all its magical computations.

plot

logical. If FALSE, nothing is plotted but the sizes are returned.

ncol

the number of columns in which to set the legend items (default is 1, a vertical legend).

horiz

logical; if TRUE, set the legend horizontally rather than vertically (specifying horiz overrides the ncol specification).

title

a character string or length-one expression giving a title to be placed at the top of the legend. Other objects will be coerced by as.graphicsAnnot.

inset

inset distance(s) from the margins as a fraction of the plot region when legend is placed by keyword.

xpd

if supplied, a value of the graphical parameter 'xpd' to be used while the legend is being drawn.

title.col

color for title.

title.adj

horizontal adjustment for title: see the help for par("adj").

seg.len

the length of lines drawn to illustrate lty and/or lwd (in units of character widths).

Details

see legend in package:graphics for details; Note: Old versions of graphics:::legend do not have ‘border’ option.