[R] Equivalent of box() in grid graphics

[Paul Murrell]

Hi

On 17/01/13 13:19, p_connolly at slingshot.co.nz wrote:
> Paul Murell's article "What's in a Name" in The R Journal Vol 4/2
> gives an interesting example of editing a stacked barplot of the barley
> data.  Using the method described in that article, it's easy to do
> something along the lines of
>
> grid.edit("plot_01.border.strip.1",
>            grep=TRUE, global=TRUE,
>            gp=gpar(col = "red"))
>
> That changes more than I'd like to change. I'd like to change only the
> bottom line of the rectangle.  How would I overwrite the unwanted red
> lines along the lines of what box() would do with base graphics?

You cannot modify just part of a basic shape (e.g., just the bottom line 
of a rectangle).  One way to do what I think you want is to specify a 
custom strip function that draws an extra line over the top of the 
existing rectangle, like this ...

library(lattice)
library(grid)
barchart(yield ~ variety | site, data = barley,
          groups = year, layout = c(1,6),
          stack = TRUE,
          ylab = "Barley Yield (bushels/acre)",
          scales = list(x = list(rot = 45)),
          strip = function(...) {
              strip.default(...)
              grid.segments(0, 0, 1, 0, gp=gpar(lwd=1.5, col="red"))
          })

Is that the sort of effect you want?

Paul

> TIA
> Patrick
>
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-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul at stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/