axis.default: Default axis annotation utilities

Description

Lattice funtions provide control over how the plot axes are annotated through a common interface. There are two levels of control. The xscale.components and yscale.components arguments can be functions that determine tick mark locations and labels given a packet. For more direct control, the axis argument can be a function that actually draws the axes. The functions documented here are the defaults for these arguments. They can additonally be used as components of user written replacements.

Usage

xscale.components.default(lim,
                          packet.number = 0,
                          packet.list = NULL,
                          top = TRUE,
                          ...)
yscale.components.default(lim,
                          packet.number = 0,
                          packet.list = NULL,
                          right = TRUE,
                          ...)
axis.default(side = c("top", "bottom", "left", "right"),
             scales, components, as.table,
             labels = c("default", "yes", "no"),
             ticks = c("default", "yes", "no"),
             ...)

Arguments

Value

xscale.components.default and yscale.components.default return a list of the form suitable as the components argument of axis.default. Valid components in the return value of xscale.components.default are:num.limitA numeric limit for the box.bottomA list with two elements, ticks and labels. ticks must be a list with components at and tck which give the location and lengths of tick marks. tck can be a vector, and will be recycled to be as long as at. labels must be a list with components at, labels, and check.overlap. at and labels give the location and labels of the tick labels; this is usually the same as the location of the ticks, but is not required to be so. check.overlap is a logical flag indicating whether overlapping of labels should be avoided by omitting some of the labels while rendering.topThis can be a logical flag; if TRUE, top is treated as being the same as bottom; if FALSE, axis annotation for the top axis is omitted. Alternatively, top can be a list like bottom.Valid components in the return value of yscale.components.default are left and right. Their interpretations are analogous to (respectively) the bottom and top components described above.

Details

These functions are part of a new API introduced in lattice 0.14 to provide the user more control over how axis annotation is done. While the API has been designed in anticipation of use that was previously unsupported, the implementation has initially focused on reproducing existing capabilities, rather then test new features. At the time of writing, several features are unimplemented. If you require them, please contact the maintainer.

Examples

Run this code

str(xscale.components.default(c(0, 1)))

set.seed(36872)
rln <- rlnorm(100)

densityplot(rln, 
            scales = list(x = list(log = 2), alternating = 3),
            xlab = "Simulated lognormal variates",
            xscale.components = function(...) {
                ans <- xscale.components.default(...)
                ans$top <- ans$bottom
                ans$bottom$labels$labels <- parse(text = ans$bottom$labels$labels)
                ans$top$labels$labels <-
                    if (require(MASS))
                        fractions(2^(ans$top$labels$at))
                    else
                        2^(ans$top$labels$at)
                ans
            })


## Direct use of axis to show two temperature scales (Celcius and
## Fahrenheit).  This does not work for multi-row plots, and doesn't
## do automatic allocation of space


F2C <- function(f) 5 * (f - 32) / 9 
C2F <- function(c) 32 + 9 * c / 5 

axis.CF <-
    function(side, ...) 
{
    ylim <- current.panel.limits()$ylim
    switch(side,
           left = {
               prettyF <- pretty(ylim)
               labF <- parse(text = sprintf("%s ~ degree * F", prettyF))
               panel.axis(side = side, outside = TRUE,
                          at = prettyF, labels = labF)
           },
           right = {
               prettyC <- pretty(F2C(ylim))
               labC <- parse(text = sprintf("%s ~ degree * C", prettyC))
               panel.axis(side = side, outside = TRUE,
                          at = C2F(prettyC), labels = labC)
           },
           axis.default(side = side, ...))
}

xyplot(nhtemp ~ time(nhtemp), aspect = "xy", type = "o",
       scales = list(y = list(alternating = 3)),
       axis = axis.CF, xlab = "Year", ylab = "Temperature", 
       main = "Yearly temperature in New Haven, CT")

## version using yscale.components

yscale.components.CF <-
    function(...)
{
    ans <- yscale.components.default(...)
    ans$right <- ans$left
    ans$left$labels$labels <-
        parse(text = sprintf("%s ~ degree * F", ans$left$labels$at))
    prettyC <- pretty(F2C(ans$num.limit))
    ans$right$ticks$at <- C2F(prettyC)
    ans$right$labels$at <- C2F(prettyC)
    ans$right$labels$labels <-
        parse(text = sprintf("%s ~ degree * C", prettyC))
    ans
}
      

xyplot(nhtemp ~ time(nhtemp), aspect = "xy", type = "o",
       scales = list(y = list(alternating = 3)),
       yscale.components = yscale.components.CF,
       xlab = "Year", ylab = "Temperature", 
       main = "Yearly temperature in New Haven, CT")

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