[R] both lines and plot characters in a lattice plot key

[Hofert Marius]

Hello,

I have two short questions concerning a key (legend) in a lattice  
plot. I have points represented by two different plot characters  
(crosses and circles) and they are colored from light to dark gray. I  
would like to have 3 parts in my legend showing the two different  
plot characters in the first two lines and the last line should  
consist of a line segment for explaining the different shades of  
gray. Below you can see what I reached so far.
My first problem is, that I do not get the 2 plot characters and the  
line segment vertically aligned to each other (I chose the vector of  
plotting characters to contain "26" as last element, because this  
leaves out a plotting character for the last line, where the line  
segment should be placed). So how do I get these aligned?
My second question is, if it's possible to have a line segment shown  
in the key, which is colored from light to dark gray (instead of a  
single color), matching the colors in my specified variable "colors"  
if possible, i.e. a single line segment starting from light gray and  
ending with a dark gray.

Thanks very much in advance!

Jan

library(lattice)
x=c(1,2,3,4,5)
y=c(5,4,3,2,1)
symbolvec=c(3,3,3,1,3)
colorseq=seq(0.25,0.88,length=5)
colors=gray(colorseq)
colorvec=colors
xyplot(y~x,
	panel=function(...){
		panel.xyplot(...,type="n")
		lpoints(x,y,pch=symbolvec,col=colorvec)
	},
key=list(x=0.2,y=0.2,lines=list(lty=c(0,0,1)),points=list(pch=c 
(1,3,26)),text=list(c("key 1","key 2","key 3")),align=T,transparent=T))