[R] Plotting second axes outside xyplot

[Paul Murrell]

Hi


Andrew Robinson wrote:
> Hi all,
> 
> I'm trying to find a way to get xyplot to produce a second set of axes outside the right hand side of the graph.  This is my progress so far:
> 
> EE <- equal.count(ethanol$E, number=9, overlap=1/4)
> xyplot(NOx ~ C | EE, data = ethanol,
>        prepanel = function(x, y) prepanel.loess(x, y, span = 1),
>        xlab = "Compression Ratio", ylab = "NOx (micrograms/J)",
>        panel = function(x, y) {
>             panel.grid(h=-1, v= 2)
>             panel.xyplot(x, y)
>             panel.loess(x,y, span=1)
>             panel.axis(side = "right", at = c(1, 3),
>                   labels = c(1, 3), outside = T)
>             },
>         aspect = "xy")
> 
> Does anyone have any suggestions?


I suspect the output from panel.axis() is getting clipped.  You might 
get it to work as follows ...

EE <- equal.count(ethanol$E, number=9, overlap=1/4)
xyplot(NOx ~ C | EE, data = ethanol,
        prepanel = function(x, y) {
          prepanel.loess(x, y, span = 1)
        },
        xlab = "Compression Ratio",
        ylab = "NOx (micrograms/J)",
        panel = function(x, y) {
          panel.grid(h=-1, v= 2)
          panel.xyplot(x, y)
          panel.loess(x,y, span=1)
          # don't call panel.axis in here
        },
        aspect = "xy")
# return to the right-most panel WITH CLIPPING OFF
trellis.focus("panel", 9, 1, clip.off=TRUE)
# draw the extra axis
panel.axis(side = "right", at = c(1, 3),
            labels = c(1, 3), outside = T)
trellis.unfocus()


Paul
-- 
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/