[R] Key titles in Lattice

[Sundar Dorai-Raj]

Kuhn, Max wrote:
> Hi,
> 
> I'm creating some lattice plots that have a key and I'd like to put a
> label on the key. The problem is that the text label for the key
> prevents the values of the group variables from being shown (see example
> below). I don't think that this is a feature, but I might be abusing the
> title arg for key.
> 
> I'm using R Version 2.3.0 (2006-04-24) on Windows XP and lattice V0.13-8
> 
> Thanks,
> 
> Max
> 
> 
> library(lattice)
> testData <- expand.grid(
>    A = letters[1:2], 
>    B = letters[3:4], 
>    C = letters[5:6])
> testData$y <- rnorm(dim(testData)[1])
> 
> stripplot(
>    y ~ A|B,  data = testData,
>    groups = C,
>    panel = function(x, y, groups, subscripts)
>    {
>       group.values <- sort(unique(groups))
>       for (i in seq(along=group.values)) 
>       {
>          id <- (groups[subscripts] == group.values[i])
>          current.val <- group.values[i]
>          panel.stripplot(x[id], y[id],
>             jitter.data = FALSE, horizontal = FALSE,
>             col = trellis.par.get()$superpose.symbol$col[i], 
>             pch = trellis.par.get()$superpose.symbol$pch[i])
>          panel.linejoin(
>             x[id], y[id], horizontal=F,
>             col = trellis.par.get()$superpose.symbol$col[i], 
>             lty = trellis.par.get()$superpose.line$lty[i], 
>             lwd = trellis.par.get()$superpose.line$lwd[i])
>       }
>    }, 
>    main = "Some Text", 
>    key = list(
>       columns = 2,
>       text=list(
> # comment the next line out to see 
> # the values of the grouping variable
>          title = "More Text",  
>          lab = letters[5:6]),
>       lines=list(
>          col = trellis.par.get()$superpose.symbol$col[1:2],
>          lwd = trellis.par.get()$superpose.line$lwd[1:2],
>          lty = trellis.par.get()$superpose.line$lty[1:2]),
>       points = list(
>          col = trellis.par.get()$superpose.symbol$col[1:2],
>          pch = trellis.par.get()$superpose.symbol$pch[1:2]))) 
> 
> ----------------------------------------------------------------------
> LEGAL NOTICE\ Unless expressly stated otherwise, this messag...{{dropped}}
> 


Hi, Max,

I think you missed this in ?xyplot under the "key" arguement:

           The '"text"' component has to have a character or expression
           vector as its first component, and the length of this vector
           determines the number of rows.

I don't see any documentation on "text" allowing a "title" element.  If 
you want to do what I think you want, try this key instead:

    key = list(
       columns = 2,
       text=list(
          c(paste("More Text", letters[5], sep = "    "), letters[6])),
       lines=list(
          col = trellis.par.get()$superpose.symbol$col[1:2],
          lwd = trellis.par.get()$superpose.line$lwd[1:2],
          lty = trellis.par.get()$superpose.line$lty[1:2]),
       points = list(
          col = trellis.par.get()$superpose.symbol$col[1:2],
          pch = trellis.par.get()$superpose.symbol$pch[1:2]))

It's not pretty, but you get idea. Perhaps others might have better 
solutions.

--sundar