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Last data update: 2014.03.03

R: Compute Pretty Axis Tick Scales

axisTicks

R Documentation

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`.

Details

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

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]`.

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

Results


R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

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Type 'demo()' for some demos, 'help()' for on-line help, or
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> library(grDevices)
> png(filename="/home/ddbj/snapshot/RGM3/R_rel/result/grDevices/axisTicks.Rd_%03d_medium.png", width=480, height=480)
> ### Name: axisTicks
> ### Title: Compute Pretty Axis Tick Scales
> ### Aliases: axisTicks .axisPars
> ### Keywords: dplot
> 
> ### ** Examples
> 
> ##--- Demonstrating correspondence between graphics'
> ##--- axis() and the graphics-engine agnostic  axisTicks() :
> 
> require("graphics")
> plot(10*(0:10)); (pu <- par("usr"))
[1]   0.6  11.4  -4.0 104.0
> 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
[1]  2  4  6  8 10
> aX(2, print(ya <- axisTicks(pu[3:4], log = FALSE)))  # y axis
[1]   0  20  40  60  80 100
> 
> axisTicks(pu[3:4], log = FALSE, n = 10)
 [1]   0  10  20  30  40  50  60  70  80  90 100
> 
> plot(10*(0:10), log = "y"); (pu <- par("usr"))
Warning message:
In xy.coords(x, y, xlabel, ylabel, log) :
  1 y value <= 0 omitted from logarithmic plot
[1]  0.60 11.40  0.96  2.04
> aX(2, print(ya <- axisTicks(pu[3:4], log = TRUE)))  # y axis
[1]  10  20  50 100
> 
> plot(2^(0:9), log = "y"); (pu <- par("usr"))
[1]  0.6400000 10.3600000 -0.1083708  2.8176408
> aX(2, print(ya <- axisTicks(pu[3:4], log = TRUE)))  # y axis
[1]   1   2   5  10  20  50 100 200 500
> 
> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>