lattice (version 0.16-2)

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"),
             ...)

Value

xscale.components.default and yscale.components.default return lists in a specific format expected by axis.default. The exact form will be documented later.

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.

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")