[R] Lattice: choice of symbol and symbol position in legend

[Peter Ehlers]

On 2011-07-26 08:47, marcel wrote:
> I am making final adjustments to a multi-plot figure using basic and lattice.
> In the lattice plot, I would like to include a legend that matches the
> format of the legends in the other plots, which consist of appropriately
> colored squares (pch 22) followed by text. In lattice, I was able to get a
> legend using
>
> auto.key = list(x = .6, y = .6, corner = c(0, 0), pch=22)
>
> but my request for pch=22 was ignored, the colors did not seem to match the
> bars exactly, and the positioning was 'text' followed by 'symbol' instead of
> the other way around. I looked through the help sections but did not find
> any detailed documentation on this. Can these be adjusted? Many thanks.

For final plots I usually prefer the more flexible key().
Here's an example using the iris data; presumably you want
pch=22 for the plotting character as well. Otherwise, you
can replace the par.settings list with simply col=c(2,3,4).

   xyplot(Sepal.Length ~ Petal.Length, groups = Species,
    data = iris,
    par.settings = list(superpose.symbol = list(
                     col = c(2,4,3),
                     pch = 22,
                     fill = "transparent")),
    key = list(x = .1, y = .8, corner = c(0, 0),
            points = list(pch=22, col=c(2,4,3), cex=1.5),
            text = list(levels(iris$Species))))

?xyplot gives a number of other key() parameters that can be
adjusted.

Peter Ehlers

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