grDevices (version 3.2.0)

axisTicks: Compute Pretty Axis Tick Scales

Description

Compute pretty axis scales and tick mark locations, the same way as traditional R graphics do it. This is interesting particularly for log scale axes.

Usage

axisTicks(usr, log, axp = NULL, nint = 5) .axisPars(usr, log = FALSE, nintLog = 5)

Arguments

usr

numeric vector of length 2, with c(min, max) axis extents.

log

logical indicating if a log scale is (thought to be) in use.

axp

numeric vector of length 3, c(mi, ma, n.), with identical meaning to par("?axp") (where ? is x or y), namely “pretty” axis extents, and an integer code n..

nint, nintLog

positive integer value indicating (approximately) the desired number of intervals. nintLog is used only for the case log = TRUE.

Value

axisTicks() returns a numeric vector of potential axis tick locations, of length approximately nint+1..axisPars() returns a list with components

axp

numeric vector of length 2, c(min., max.), of pretty axis extents.

n

integer (code), with the same meaning as par("?axp")[3].

Details

axisTicks(usr, *) calls .axisPars(usr, ..) when axp is missing (or NULL).

See Also

axTicks; axis, and par (from the graphics package).

Examples

##--- Demonstrating correspondence between graphics'
##--- axis() and the graphics-engine agnostic  axisTicks() :

require("graphics")
plot(10*(0:10)); (pu <- par("usr"))
aX <- function(side, at, ...)
    axis(side, at = at, labels = FALSE, lwd.ticks = 2, col.ticks = 2,
         tck = 0.05, ...)
aX(1, print(xa <- axisTicks(pu[1:2], log = FALSE)))  # x axis
aX(2, print(ya <- axisTicks(pu[3:4], log = FALSE)))  # y axis

axisTicks(pu[3:4], log = FALSE, n = 10)

plot(10*(0:10), log = "y"); (pu <- par("usr"))
aX(2, print(ya <- axisTicks(pu[3:4], log = TRUE)))  # y axis

plot(2^(0:9), log = "y"); (pu <- par("usr"))
aX(2, print(ya <- axisTicks(pu[3:4], log = TRUE)))  # y axis