[R] How to overlay lines and rectangles in lattice plot key

[Richard M. Heiberger]

Yes, but it will probably require work.  I think you will need to
write a grob that does what you want
and then use the grob in a legend statement in the xyplot.

Start with the 'legend' argument to xyplot (about line 940 in ?xyplot).
You will probably need to work directly with grid functions and will
find Paul Murrell's book very helpful.
https://www.crcpress.com/R-Graphics/Murrell/p/book/9781584884866

Rich

On Wed, Dec 28, 2016 at 9:50 PM, sbihorel
<Sebastien.Bihorel at cognigencorp.com> wrote:
> Hi,
>
> I would like to create a custom key for a lattice xyplot in which line
> elements are displayed on top of rectangle elements. In the example code
> below, the lines and rectangles are shown side by side (the legend itself is
> meaningless, but that is not the point). Is there a way to overlay these key
> elements (but not the text)?
>
> Thanks
>
> xyplot(Sepal.Length + Sepal.Width ~ Petal.Length + Petal.Width,
>   iris,
>   type = c("p", "r"),
>   jitter.x = TRUE,
>   jitter.y = TRUE,
>   factor = 5,
>   key = list(
>     column=4,
>     text=list(lab=letters[1:4]),
>     lines=list(col=1:4, pch=1:4, type='b'),
>     rectangles=list(col=1:4, alpha=0.25, border=FALSE)
>   )
> )
>
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