[R] lattice key inside panel

[Iago Mosqueira]

Deepayan Sarkar wrote:
> On Wed, Feb 4, 2009 at 8:21 AM, Iago Mosqueira <iago.mosqueira at gmail.com> wrote:
>> Hello,
>>
>> I am trying to draw a key inside a single panel in a lattice xyplot. The
>> panel function uses panel.number() to use a slightly different style for
>> one of the panels. Once inside than panel I am using
>>
>> draw.key(list(text=list(lab='catch'),
>>          lines=list(lwd=c(2)),
>>          text=list(lab='landings'),
>>          rectangles=list(col=rgb(0.1, 0.1, 0, 0.1)),
>>         x=0, y=1, corner=c(0,0)), draw=TRUE)
>>
>> which gets me the key right in the middle of the panel. I would like to
>> have at the top or bottom. Changes to the values of x, y or corner do
>> not seem to change the position at all.
>>
>> lattice.getOption("legend.bbox") returns 'panel'.
>>
>> I am quit sure I am missing something essential, but can this be done
>> without calling directly grid methods?
> 
> No. The placement controls such as x, y, and corner are not handled by
> draw.key itself, but rather by the high-level plotting function. Used
> directly, draw.key() basically gives you a low-level grid "grob", and
> you need to use grid tools to do anything with them ('draw=TRUE'
> simply calls grid.draw() on the grob before returning it). The
> simplest way to change position is to supply a simple 'vp' argument.
> 
> xyplot(1~1,
>        panel = function(...) {
>            require(grid)
>            panel.xyplot(...)
>            draw.key(list(text=list(lab='catch'),
>                          lines=list(lwd=c(2)),
>                          text=list(lab='landings'),
>                          rectangles=list(col=rgb(0.1, 0.1, 0, 0.1))),
>                     draw = TRUE,
>                     vp = viewport(x = unit(0.75, "npc"), y = unit(0.9, "npc")))
>        })
> 
>  More complex positioning (perhaps depending on the size of the
> legend) will need more work.
> 
> -Deepayan

Thanks so much. This works perfectly.

One other thing that has so far eluded me is how to specify two
different kinds of symbols on a single column. The key above shows

text line text rectangle

but I would really like to get

text line
text rectangle

but this did not seem possible to me. Am I wrong?

Thanks,


Iago