R help - Dec 2008 - legend idea for latticeExtra

Dear list,


I've written a small utility function to add arbitrary legend(s) to a  
lattice graph (or a combination of them), much like the legend  
function of base graphics. I though perhaps it could be useful to  
someone else, or improved by suggestions. I understand this goes  
against the lattice paradigm somewhat, in that you short-cut the link  
between group variables and the appearance of the legend. There are  
some cases where I was missing this kind of raw command, though, and  
the custom legend dendrogram of the lattice book is intimidating if  
not a bit overkill.

llegend <- function(x=0.5, y=0.5, loc=FALSE, text=c("a",
"b"),
unit="npc",
					pch=1, lty=NULL, col=seq_along(text), cex=0.6,  
cex.title=0.8,  ...){
	if(loc) {
		ll <- grid.locator(unit)
		print(ll)
		x <- as.numeric(ll$x)
		y <- as.numeric(ll$y)
		}
lines <- !is.null(lty)
points <- !is.null(pch)

	keyGrob <- draw.key(key=simpleKey(text, lines=lines,
							points = points,cex=cex, cex.title=cex.title, ...),
						vp=viewport(x=unit(x, unit), y=unit(y, unit)), draw=F)
	grid.draw(keyGrob)
	invisible(keyGrob)
}

# example (locator used for the second legend)
xyplot(1~1)
llegend()
llegend(loc=T, title="Here goes another") # click wherever on the  
viewport.


Best wishes,

baptiste
_____________________________

Baptiste Augui?

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag

On 12/2/08, baptiste auguie <ba208 at exeter.ac.uk>
wrote:
> Dear list,
>
>
>  I've written a small utility function to add arbitrary legend(s) to a
> lattice graph (or a combination of them), much like the legend function of
> base graphics. I though perhaps it could be useful to someone else, or
> improved by suggestions. I understand this goes against the lattice
paradigm
> somewhat, in that you short-cut the link between group variables and the
> appearance of the legend. There are some cases where I was missing this
kind
> of raw command, though, and the custom legend dendrogram of the lattice
book
> is intimidating if not a bit overkill.
The book has a similar example:

data(Chem97, package = "mlmRev")

## Figure 12.1
qqmath(~ gcsescore | factor(score), Chem97, groups = gender,
       f.value = function(n) ppoints(100),
       aspect = "xy",
       page = function(n) {
           cat("Click on plot to place legend", fill = TRUE)
           ll <- grid.locator(unit = "npc")
           if (!is.null(ll))
               draw.key(simpleKey(levels(factor(Chem97$gender))),
                        vp = viewport(x = ll$x, y = ll$y),
                        draw = TRUE)
       })

I will consider adding a version of this in latticeExtra (both this
and your example are not sufficiently general in their present form).

-Deepayan
>  llegend <- function(x=0.5, y=0.5, loc=FALSE, text=c("a",
"b"), unit="npc",
>                                         pch=1, lty=NULL,
> col=seq_along(text), cex=0.6, cex.title=0.8,  ...){
>         if(loc) {
>                 ll <- grid.locator(unit)
>                 print(ll)
>                 x <- as.numeric(ll$x)
>                 y <- as.numeric(ll$y)
>                 }
>  lines <- !is.null(lty)
>  points <- !is.null(pch)
>
>         keyGrob <- draw.key(key=simpleKey(text, lines=lines,
>                                                         points >
points,cex=cex, cex.title=cex.title, ...),
>                                                 vp=viewport(x=unit(x,
unit),
> y=unit(y, unit)), draw=F)
>         grid.draw(keyGrob)
>         invisible(keyGrob)
>  }
>
>  # example (locator used for the second legend)
>  xyplot(1~1)
>  llegend()
>  llegend(loc=T, title="Here goes another") # click wherever on
the viewport.
>
>
>  Best wishes,
>
>  baptiste
>  _____________________________
>
>  Baptiste Augui?
>
>  School of Physics
>  University of Exeter
>  Stocker Road,
>  Exeter, Devon,
>  EX4 4QL, UK
>
>  Phone: +44 1392 264187
>
>  http://newton.ex.ac.uk/research/emag
>
>  ______________________________________________
>  R-help at r-project.org mailing list
>  https://stat.ethz.ch/mailman/listinfo/r-help
>  PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
>  and provide commented, minimal, self-contained, reproducible code.
>