scale caption on levelplot
Andrew, see below
On 2010-12-04 08:25, David Winsemius wrote:
On Dec 4, 2010, at 8:25 AM, Andrew Collier wrote:
hi, i am trying to figure out how to put a caption on the colour scale of a levelplot. there does not seem to be an option for this in levelplot().
Agreed. I could not find one in the levelplot help page or in the chapter of Lattice on legends and keys. Sarkar basically says you need to use grid calls if you want to go beyond the basics.
i tried using mtext() but as soon as you put the text far out enough on the right of the plot, it goes beyond the plot boundary. so i tried to extend the margin on the right of the plot using par(mar) but this did not have any effect on the plot area. i would really appreciate some help with this because having a caption on a colour scale is rather fundamental and certainly something that a journal referee is going to pick up on!
Your question has no reproducible example but suggests that you do not
understand that levelplot is a lattice function and that lattice uses
grid graphics. The par arguments that lattice understands (or is
willing to deal with gracefully) are passed through trellis.par.set().
The current settings are accessible with:
trellis.par.get()
Since lattice is implemented with grid graphics, you may get useful
information from:
require(grid) # lattice apparently loads gpar and its help page but
doesn't
# actually load grid. (I don't understand this. )
?gpar() # Which has examples that may allow you to get a better
understanding
# of how to layer new material on top of existing grid
graphics.
As David says, you need to use trellis parameters, in this case
presumably trellis.par.get('layout.widths') and
trellis.par.get('layout.heights') will be useful. You can add
appropriate settings to your levelplot() call with the
par.settings argument. After you adjust the amount of space
you want, you can then use grid::grid.text() to add your text.
Here's an example:
library(grid)
x <- sort(rnorm(100,50,10))
y <- sort(runif(100,0,20))
d <- expand.grid(x=x, y=y)
d$z <- x + y
graphics.off()
p <- levelplot(z ~ x*y, d,
par.settings=list(
layout.widths=list(right.padding=4),
layout.heights=list(top.padding=6)),
colorkey = TRUE)
print(p)
## now add the text
grid.text('here and there', x=.98, y=.5, rot=-90,
gp = gpar(col=4,
fontfamily="HersheyGothicEnglish", cex=2))
grid.text('here\nand\nthere', x=.88, y=.92,
gp = gpar(lineheight=.75, col=3))
Peter Ehlers