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

[Deepayan Sarkar]

On 6/14/06, Benjamin Tyner <btyner at gmail.com> 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

For the record, one alternative is something like


with(cars.lo,
     xyplot(residuals + fitted ~ x,
            strip=FALSE, strip.left = TRUE,
            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")
                   }
            }))


> 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 single viewort for ylab, which you can get to with

downViewport(trellis.vpname("ylab"))

or

trellis.focus("ylab")

(the latter currently doesn't work because of a bug). This viewport
spans all the panels, but you could place your labels suitably if you
know how many rows of panels you have. BTW, ylab = "" may not actually
create this viewport, but ylab = " " should be safe.

Deepayan