Legend in xyplot two columns

Thanks Deepayan!

Your solution does excatly what I want. 
Further experiments and thoughts on my side brought me also to a
solution. 
If I use the option rep=FALSE, and plot the bullit with "lines" and
split the "lines" argument into two groups it gives me the same result,
as every item in the key list starts a new column.

library(lattice)
key <- list( rep=FALSE,
               lines=list(col=c("red", "blue"), type=c("p","l"),
pch=19),
               text=list(lab=c("John","Paul")),
               lines=list(col=c("green", "red"), type=c("l", "l")),
               text=list(lab=c("George","Ringo")),
               rectangles = list(col= "#FFFFCC", border=FALSE),
               text=list(lab="The Beatles"),
		   )

xyplot(1~1, key=key)


But your solution is much more felxible!

Kind Regards

Markus

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From: Deepayan Sarkar [mailto:deepayan at stat.wisc.edu] 
Sent: 14 April 2005 16:01
To: r-help at stat.math.ethz.ch
Cc: Gesmann, Markus
Subject: Re: [R] Legend in xyplot two columns

Dear R-Help

I have some trouble to set the legend in a xyplot into two rows.
The code below gives me the legend in the layout I am looking for, I
just rather have it in two rows.

library(lattice)
schluessel <- list(
               points=list( col="red", pch=19, cex=0.5 ),
               text=list(lab="John"),
               lines=list(col="blue"),
               text=list(lab="Paul"),
               lines=list(col="green"),
               text=list(lab="George"),
               lines=list(col="orange"),
               text=list(lab="Ringo"),
               rectangles = list(col= "#FFFFCC", border=FALSE),
               text=list(lab="The Beatles"),
     )

xyplot(1~1, key=schluessel)

The next code gives me two rows, but repeates all the points,lines,
and rectangles.

schluessel2 <- list(
               points=list( col="red", pch=19, cex=0.5 ),
               lines=list(col=c("blue", "green", "orange")),
               rectangles = list(col= "#FFFFCC", border=FALSE),
               text=list(lab=c("John","Paul","George","Ringo", "The
Beatles")),
               columns=3,
      )

xyplot(1~1, key=schluessel2)

So I think each list has to have 6 items, but some with "no" content.
How do I do this?

You could try using col="transparent" to suppress things, but that's not

a very satisfactory solution. The function to create the key is simply 
not designed to create unstructured legends like this. However, you can 
create an use an arbitrary ``grob'' (grid graphics object) for a 
legend, e.g.:

##-----------------

library(grid)
library(lattice)

fl <-
    grid.layout(nrow = 2, ncol = 6,
                heights = unit(rep(1, 2), "lines"),
                widths =
                unit(c(2, 1, 2, 1, 2, 1),
                     c("cm", "strwidth", "cm",
                       "strwidth", "cm", "strwidth"),
                     data = list(NULL, "John", NULL,
                     "George", NULL, "The Beatles")))

foo <- frameGrob(layout = fl)
foo <- placeGrob(foo,
                 pointsGrob(.5, .5, pch=19,
                            gp = gpar(col="red", cex=0.5)),
                 row = 1, col = 1)
foo <- placeGrob(foo,
                 linesGrob(c(0.2, 0.8), c(.5, .5),
                           gp = gpar(col="blue")),
                 row = 2, col = 1)
foo <- placeGrob(foo,
                 linesGrob(c(0.2, 0.8), c(.5, .5),
                           gp = gpar(col="green")), 
                 row = 1, col = 3)
foo <- placeGrob(foo,
                 linesGrob(c(0.2, 0.8), c(.5, .5),
                           gp = gpar(col="orange")), 
                 row = 2, col = 3)
foo <- placeGrob(foo,
                 rectGrob(width = 0.6, 
                          gp = gpar(col="#FFFFCC",
                          fill = "#FFFFCC")), 
                 row = 1, col = 5)
foo <- placeGrob(foo,
                 textGrob(lab = "John"), 
                 row = 1, col = 2)
foo <- placeGrob(foo,
                 textGrob(lab = "Paul"), 
                 row = 2, col = 2)
foo <- placeGrob(foo,
                 textGrob(lab = "George"), 
                 row = 1, col = 4)
foo <- placeGrob(foo,
                 textGrob(lab = "Ringo"), 
                 row = 2, col = 4)
foo <- placeGrob(foo,
                 textGrob(lab = "The Beatles"), 
                 row = 1, col = 6)

xyplot(1 ~ 1, legend = list(top = list(fun = foo)))

##-----------------

HTH,

Deepayan