legend {base}

R Documentation

Add Legends to Plots

Description

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

The default values for x.intersp and y.intersp are computed from Cx <- cex * par('cex').

Usage

legend(x, y, legend, fill, col= "black", lty, pch, bty = "o",
       bg = par("bg"), cex = 1, xjust = 0, yjust = 1,
       x.intersp = NULL, y.intersp = NULL, text.width = NULL, merge = FALSE)

Arguments

x	the x location of the legend.
y	the y location of the legend.
legend	a vector of text values or an expression of length \ge 1 to appear in the legend.
fill	if specied, this argument will cause boxes filled with the specified colors to appear beside the legend text.
col	the color of points or lines appearing in the legend.
lty	the line types for lines appearing in the legend.
pch	the plotting symbols appearing in the legend.
bty	the type of box to be drawn around the legend.
bg	the background color for the legend box.
cex	character expansion factor relative to current par("cex").
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 as x.intersp for vertical (y) line distances.
text.width	the width of the legend text in x ("user") coordinates. Defaults to the proper value computed by strwidth(legend).
merge	logical; if TRUE, “merge” points and lines but not filled boxes.

See Also

plot, barplot which uses legend(), and text for more examples of math expressions.

Examples

# Run the example in `?matplot' or the following:
matplot(c(1,8), c(0,4.5), type = "n", xlab = "Length", ylab = "Width",
        main = "Petal and Sepal Dimensions in Iris Blossoms")
leg.txt <- c("    Setosa Petals", "    Setosa Sepals",
             "Versicolor Petals", "Versicolor Sepals")
y.leg <- c( 4, 3, 2.2, 1.5, .9)
cexv  <- c( 1, .8, .6, .4, .25)
for (i in seq(cexv))
  legend(1, y.leg[i], leg.txt, pch = "sSvV", col = c(1, 3), cex = cexv[i])

# `merge = TRUE' for merging lines & points:
x <- seq(-pi, pi, len = 65)
plot(x, sin(x), type = "l", ylim = c(-1.2, 1.8), col = 3, lty = 2)
points(x, cos(x), pch = 3, col = 5)
lines(x, tan(x), type = "b", lty = 1, pch = 4, col = 9)
title("legend(..... lty = c(2, -1, 1), pch = c(-1,3,4), merge = TRUE)",
      cex.main = 1.1)
vcex <- c( 3,1.5, 1,   .8)
vx   <- c(-2,  0, 1.5, 2.8)
for (i in seq(vcex))
  legend(vx[i], 1.8, c("sin", "cos", "tan"), xjust = .5, col = c(3, 5, 9),
         lty = c(2, -1, 1), pch = c(-1, 3, 4), merge = TRUE, cex = vcex[i])

##-- Math expressions:
plot (x, sin(x), type="l", col = 2, xlab = expression(phi))
lines(x, cos(x), col = 3, lty = 2); abline(h=0, v=pi/2*(-6:6), col="gray90")
ex.cs1 <- expression(plain(sin) * phi,  plain(cos) * phi)
ex.cs2 <- expression(paste("sin ",phi), paste("cos ",phi))
legend(-3, .9, ex.cs1, lty=1:2, col=2:3)

x <- rexp(100, rate = .5)
hist(x, main = "Mean and Median of a Skewed Distribution")
abline(v = mean(x),   col=2, lty=2, lwd=2)
abline(v = median(x), col=3, lty=3, lwd=2)
ex12 <- expression(bar(x) == sum(over(x[i], n), i==1, n),
    		   hat(x) == median(x[i], i==1,n))
legend(4,30, ex12, col = 2:3, lty=2:3) # lwd = 2 does not yet work
rm(x, ex12, ex.cs1, ex.cs2)

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