On Fri, May 8, 2009 at 8:08 AM, Paul Boutros <paul.bout...@utoronto.ca> wrote:
> Hello,
>
> I'm attempting to alter the location of text in my axis labels in lattice
> plots and have been unsuccessful so far. For example, the y-axis labels are
> always right-justified, but I would like them to be horizontally centered.
>
> Here's an example:
> library(lattice);
>
> # create fake dataset to plot
> to.plot <- data.frame(
> x = 1:5,
> y = c("1\nAAA", "2\nBBB", "3\nCCC", "4\nDDD", "5\nEEE")
> );
>
> # initial plot, note that the y-axis labels are right-justified
> xyplot(
> y ~ x,
> to.plot,
> pch = 19,
> ylab = "",
> xlab = "",
> cex = 3
> );
>
> # now try to set the positioning via scales
> xyplot(
> y ~ x,
> to.plot,
> pch = 19,
> ylab = "",
> xlab = "",
> cex = 3,
> scales = list(
> labels = to.plot$y,
> hjust = 0.5,
> vjust = 0.5
> )
> );
>
> I also explored using yscale.components.default(), but specifying hjust and
> vjust there did not help. Any suggestions would be very much appreciated!
The justification calculations are hard-coded in the default axis
function 'axis.default' (mainly to handle rotated labels). You can
provide your own axis function to override this. A general replacement
would be a lot more complicated, but this should suffice for your
example (it could be simplified further if you don't care about tick
marks).
axis.y <- function(side, components, ...)
{
if (side == "left")
{
require(grid)
str(components)
axis.units <- lattice.getOption("axis.units")[["outer"]][["left"]]
axis.settings <- trellis.par.get("axis.components")[["left"]]
tck.unit.x <- components$left$ticks$tck *
axis.settings$tck * axis.units$tick$x
tck.unit <- unit(x = tck.unit.x, units = axis.units$tick$units)
with(components$left$ticks,
{
grid.segments(y0 = unit(at, "native"),
y1 = unit(at, "native"),
x0 = unit(0, "npc"),
x1 = -1 * tck.unit)
})
with(components$left$labels,
{
lab.unit <- tck.unit +
unit(x = axis.settings$pad1 * axis.units$pad1$x,
units = axis.units$pad1$units) +
0.5 * unit(1, "grobwidth", textGrob(labels))
grid.text(label = labels,
y = unit(at, "native"),
x = -1 * lab.unit,
just = "center")
})
}
else axis.default(side = side,
components = components,
...)
}
xyplot(y ~ x,
to.plot,
pch = 19,
ylab = "",
xlab = "",
cex = 3,
axis = axis.y)
At some point I should allow the labels to be "grobs", which should
make things like this a bit simpler.
-Deepayan
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