Add Error Bars to an Existing Plot

Add error bars to an existing plot.

ErrBars(from, to = NULL, pos = NULL, mid = NULL, horiz = FALSE, col = par("fg"),
        lty = par("lty"), lwd = par("lwd"), code = 3, length = 0.05,
        pch = NA, cex.pch = par("cex"), col.pch = par("fg"), bg.pch = par("bg"),
        ...)

Arguments

from

coordinates of points from which to draw (the lower end of the error bars). If to is left to NULL and from is a \(k \times 2 \) dimensional matrix, the first column will be interpreted as from and the second as to.

to

coordinates of points to which to draw (the upper end of the error bars).

pos

numeric, position of the error bars. This will either be the x-coordinate in case of vertical error bars and the y-coordinate in case of horizontal error bars.

mid

numeric, position of midpoints. Defaults to the mean of from and to.

horiz

logical, determining whether horizontal error bars are needed (default is FALSE).

col

the line color.

lty

the line type.

lwd

line width.

code

integer code, determining where end lines are to be drawn. code = 0 will draw no end lines, code = 1 will draw an end line on the left (lower) side at (x0[i], y0[i]), code = 2 on the right (upper) side (x1[i], y1[i]) and code = 3 (default) will draw end lines at both ends.

length

the length of the end lines.

pch

plotting character for the midpoints. The position of the points is given by mid. If mid is left to NULL the points will be plotted in the middle of from and to. No points will be plotted if this is set to NA, which is the default.

cex.pch

the character extension for the plotting characters. Default is par("cex").

col.pch

the color of the plotting characters. Default is par("fg").

bg.pch

the background color of the plotting characters (if pch is set to 21:25). Default is par("bg").

...

the dots are passed to the arrows function.

Details

A short wrapper for plotting error bars by means of arrows.

Author

Andri Signorell <andri@signorell.net>

See also

arrows, lines.loess

Examples

par(mfrow=c(2,2))
b <- barplot(1:5, ylim=c(0,6))
ErrBars(from=1:5-rep(0.5,5), to=1:5+rep(0.5,5), pos=b, length=0.2)

# just on one side
b <- barplot(1:5, ylim=c(0,6))
ErrBars(from=1:5, to=1:5+rep(0.5,5), pos=b, length=0.2, col="red", code=2, lwd=2)

b <- barplot(1:5, xlim=c(0,6), horiz=TRUE)
ErrBars(from=1:5, to=1:5+rep(0.2,5), pos=b, horiz=TRUE,  length=0.2, col="red", code=2, lwd=2)

par(xpd=FALSE)
dotchart(1:5, xlim=c(0,6))
ErrBars(from=1:5-rep(0.2,5), to=1:5+rep(0.2,5), horiz=TRUE, length=0.1)