[R] lattice key (legend) with both points and lines

[Sundar Dorai-Raj]

Peter McMahan said the following on 3/20/2007 3:16 PM:
> Hello,
> I'm running into a frustrating problem with the legend on a lattice  
> plot I'm working with. The plot is a stripplot with a panel.linejoin 
> () line running through the mean of each of the categories. Thus  
> there are both points and lines in the plot.
> In trying to make a key for the plot, I can't figure out how to make  
> a legend for both the points and the lines. What I'd like is  
> something like:
> 
> prices    *
> means   -----
> 
> in which there are two "rows" in the legend, one with the point and  
> its label and one with the line and its label. By supplying this type  
> of argument to stripplot:
> 
> key=list(text=list(lab="prices"),
>           points=list(...),
>           text=list(lab="means"),
>           lines=list(...))
> 
> I can get a legend that looks like:
> 
> prices    *     means   -----
> 
> But this looks awkward with my plot
> 
> Is there any way to have the plot elements and their labels be in the  
> same column?
> 
> Thanks,
> Peter
> 
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You can try:

library(lattice)
xyplot(1:10 ~ 1:10,
        key = list(text = list(c("prices", "means")),
                  lines = list(
                    pch = c("*", ""), type = c("p", "l"),
                    cex = 2, col = "red", lwd = 3)))

HTH,

--sundar