[R] positioning of separate y-axis labels in xyplot

[Paul Murrell]

Hi


Benjamin Tyner wrote:
> I like the functionality provided by outer=TRUE, but when it comes time 
> to place separate xlabs or ylabs, I always end up 'eyeballing' it on a 
> case-by-case basis. For example,
> 
> ##begin example
> require(lattice)
> 
> cars.lo <- loess(dist ~ speed, cars)
> 
> print(xyplot(cars.lo$residuals+cars.lo$fitted~cars.lo$x,
>              strip=FALSE,
>              outer=TRUE,
>              layout=c(1,2),
>              ylab="",
>              scales=list(y=list(relation="free",rot=0)),
>              panel=function(x,y,panel.number,...){
>                    if(panel.number==1){
>                       panel.xyplot(x,y)
>                       panel.abline(h=0)
>                    }else{
>                       panel.xyplot(x,y=cars.lo$y)
>                       panel.xyplot(x,y,type="l")
>                    }
>              }))
> 
> require(grid)
> trellis.focus("panel", 1, 1, clip.off=TRUE, highlight=FALSE)
> grid.text("residuals", x=unit(0, "npc") + unit(-2, "lines"),rot=90)
> trellis.focus("panel", 1, 2, clip.off=TRUE, highlight=FALSE)
> grid.text("fitted", x=unit(0, "npc") + unit(-2, "lines"),rot=90)
> ## end example
> 
> In this case, a distance of -2 lines happens to be enough, but one has 
> to make the plot to know this. I'm interested in learning how one can 
> place the ylabs without fear of overlapping the tick labels; i.e., how 
> to use the exact space allocated by ylab="". I'm thinking it must 
> involve viewports?


There is a 'ylab' viewport set up by lattice, although it is just one 
big one for all panels.  Here's what you could do for your example (with 
knowledge of how many rows of panels there are) ...

downViewport(trellis.vpname("ylab"))
# If you want to see where the viewport is ...
# grid.rect(gp=gpar(col="red"), name="temp")
grid.text("residuals", y=0.25, rot=90)
grid.text("fitted", y=0.75, rot=90)
# If you want to remove the rect again ...
# grid.remove("temp")
upViewport(0)

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/