grDevices (version 3.3)

axisTicks: Compute Pretty Axis Tick Scales

Description

Compute pretty axis scales and tick mark locations, the same way as traditional Rgraphics 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

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