label.ellipse: Draw a Label on an Ellipse-like Object

Description

Draws a label on an ellipse (or similar closed ploygon object) allowing a label.pos argument to specify the position of the label as center, bottom, left, top, or right relative to the object.

Usage

label.ellipse(ellipse, label, col = "black", label.pos = NULL, 
      xpd = TRUE, tweak = 0.5 * c(strwidth("M"), strheight("M")), ...)

Arguments

ellipse

A two-column matrix, or an object that can be coerced to one.

label

Label text, a character string, or expression (or coercible to such a type).

col

Label color

label.pos

Label position, an integer (in 0:4) or character string (in c("center", "bottom", "left", "top", "right")). Values of 1, 2, 3 and 4, respectively indicate positions below, to the left of, above and to the right of the max/min

xpd

logical. Whether to allow the label to go beyond the plot area.

tweak

A two element vector specifying minor adjustments applied to the x or y coordinate of the label, depending on label.pos. The defaults are one-half the width and height of an uppercase "M" on the current graphics device. Alternatively, y

...

Other arguments passed to text, such as offset, srt, font, family, etc.

Value

None.

Details

Like text, this function simply adds to an existing base graphics plot.

Examples

Run this code

op <- par(mfrow=c(1,2))
plot(c(-2,2), c(-3,3), type="n", xlab="x", ylab="y")
E <- ellipse(c(0,0), matrix(c(1,2,2,5), 2, 2), 1, add=TRUE)

label.ellipse(E, "default", col="red", cex=2)
label.ellipse(E, "center", label.pos=0)
label.ellipse(E, "bottom", label.pos=1)
label.ellipse(E, "top", label.pos=3)
label.ellipse(E, "left", label.pos=2)
label.ellipse(E, "right", label.pos=4)

plot(c(-2,2), c(-3,3), type="n", xlab="x", ylab="y")
E <- ellipse(c(0,0), matrix(c(1,-2,-2,5), 2, 2), 1, add=TRUE)

label.ellipse(E, "default", col="red", cex=2)
label.ellipse(E, "center", label.pos="center")
label.ellipse(E, "bottom", label.pos=1, cex=1.5)
label.ellipse(E, "top", label.pos=3, cex=1.5)
label.ellipse(E, "left", label.pos=2, cex=1.5)
label.ellipse(E, "right", label.pos=4, cex=1.5)
par(op)