axis {base}

R Documentation

Add an Axis to a Plot

Description

Adds an axis to the current plot, allowing the specification of the side, position, labels, and other options.

Usage

axis(side, at = NULL, labels = TRUE, tick = TRUE, line = NA,
     pos = NA, outer = FALSE, font = NA, vfont = NULL,
     lty = "solid", lwd = 1, col = NULL, ...)

Arguments

side	an integer specifying which side of the plot the axis is to be drawn on. The axis is placed as follows: 1=below, 2=left, 3=above and 4=right.
at	the points at which tick-marks are to be drawn. Non-finite (infinite, NaN or NA) values are omitted. By default, when NULL, tickmark locations are computed, see Details below.
labels	this can either be a logical value specifying whether (numerical) annotations are to be made at the tickmarks, or a vector of character strings to be placed at the tickpoints.
tick	a logical value specifying whether tickmarks should be drawn

.

line	the number of lines into the margin which the axis will be drawn. This overrides the value of the graphical parameter mgp[3]. The relative placing of tickmarks and tick labels is unchanged.
pos	the coordinate at which the axis line is to be drawn. this overrides the value of both line and mgp[3].
outer	a logical value indicating whether the axis should be drawn in the outer plot margin, rather than the standard plot margin.
font	font for text.
vfont	vector font for text.
lty, lwd	line type, width for the axis line and the tick marks.
col	color for the axis line and the tick marks. The default NULL means to use par("fg").
...	other graphical parameters may also be passed as arguments to this function, e.g., las for vertical/horizontal label orientation, or fg instead of col, see par on these.

Details

The axis line is drawn from the lowest to the highest value of at, but will be clipped at the plot region. Only ticks which are drawn from points within the plot region (up to a tolerance for rounding error) are plotted, but the ticks and their labels may well extend outside the plot region.

When at = NULL, pretty tick mark locations are computed internally, from par("usr","lab"), and par("xlog") (or ylog respectively).

Value

This function is invoked for its side effect, which is to add an axis to an already existing plot.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth \& Brooks/Cole.

Examples

plot(1:4, rnorm(4), axes=FALSE)
axis(1, 1:4, LETTERS[1:4])
axis(2)
box() #- to make it look "as usual"

plot(1:7, rnorm(7), main = "axis() examples",
     type = "s", xaxt="n", frame = FALSE, col = "red")
axis(1, 1:7, LETTERS[1:7], col.axis = "blue")
# unusual options:
axis(4, col = "violet", col.axis="dark violet",lwd = 2)
axis(3, col = "gold", lty = 2, lwd = 0.5)

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