[R] update'ing trellis object

[David Winsemius]

On Oct 3, 2009, at 7:05 PM, Sebastian P. Luque wrote:

> Hi,
>
> I thought the following would only remove the legend element of a
> trellis object, but it actually removes both the legend and key
> elements:
>
> ---<--------------------cut here--------------- 
> start------------------->---
> fig <- xyplot(Sepal.Length ~ Petal.Length, groups=Species, data=iris,
>              key=list(x=1, y=0.02, corner=c(1, 0), size=3, between=1,
>                text=list(levels(iris$Species))),
>              legend=list(inside=list(fun="draw.key", x=0, y=1,
>                            corner=c(0, 1),
>                            args=list(key=list(text=list("a)",  
> cex=1.5)),
>                              draw=FALSE))))
> update(fig, legend=NULL)
> ---<--------------------cut here--------------- 
> end--------------------->---
>
> Is this the right way to remove an element from the object, using
> update.trellis()?  Thanks.
>
It probably depends on the element. In the case of "key", it is a  
descendant of the legend list so when you make legend NULL you are  
wiping out all of its descendants as well:
 > str(fig)
List of 43
snipped a few lines
  $ legend           :List of 2
   ..$ inside:List of 5
   .. ..$ fun   : chr "draw.key"
   .. ..$ args  :List of 2
   .. .. ..$ key :List of 6
   .. .. .. ..$ x      : num 1
   .. .. .. ..$ y      : num 0.02
   .. .. .. ..$ corner : num [1:2] 1 0
   .. .. .. ..$ size   : num 3
   .. .. .. ..$ between: num 1
   .. .. .. ..$ text   :List of 1
   .. .. .. .. ..$ : chr [1:3] "setosa" "versicolor" "virginica"
   .. .. ..$ draw: logi FALSE
   .. ..$ x     : num 1
   .. ..$ y     : num 0.02
   .. ..$ corner: num [1:2] 1 0
   ..$ inside:List of 5
   .. ..$ fun   : chr "draw.key"
   .. ..$ x     : num 0
   .. ..$ y     : num 1
   .. ..$ corner: num [1:2] 0 1
   .. ..$ args  :List of 2
   .. .. ..$ key :List of 1
   .. .. .. ..$ text:List of 2
   .. .. .. .. ..$    : chr "a)"
   .. .. .. .. ..$ cex: num 1.5
   .. .. ..$ draw: logi FALSE

>
> Cheers,
>
> -- 
> Seb
>
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