lattice (version 0.20-34)

G_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"), ..., prefix)

Arguments

lim

the range of the data in that packet (data subset corresponding to a combination of levels of the conditioning variable). The range is not necessarily numeric; e.g. for factors, they could be character vectors representing levels, and for the various date-time representations, they could be vectors of length 2 with the corresponding class.

packet.number

which packet (counted according to the packet order, described in print.trellis) is being processed. In cases where all panels have the same limits, this function is called only once (rather than once for each packet), in which case this argument will have the value 0.

packet.list

list, as long as the number of packets, giving all the actual packets. Specifically, each component is the list of arguments given to the panel function when and if that packet is drawn in a panel. (This has not yet been implemented.)

top, right

the value of the top and right components of the result, as appropriate. See below for interpretation.

side

on which side the axis is to be drawn. The usual partial matching rules apply.

scales

the appropriate component of the scales argument supplied to the high level function, suitably standardized.

components

list, similar to those produced by xscale.components.default and yscale.components.default.

as.table

the as.table argument in the high level function.

labels

whether labels are to be drawn. By default, the rules determined by scales are used.

ticks

whether labels are to be drawn. By default, the rules determined by scales are used.

...

many other arguments may be supplied, and are passed on to other internal functions.

prefix

A character string identifying the plot being drawn (see print.trellis). Used to retrieve location of current panel in the overall layout, so that axes can be drawn appropriately.

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: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 than test new features. At the time of writing, several features are unimplemented. If you require them, please contact the maintainer.

See Also

Lattice, xyplot, print.trellis

Examples

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")