[R] Lattice Cloud()-Plot with the same color for different groups

[Hofert Marius]

Hi,

Consider the following cloud()-plot consisting of two lines:

library(lattice)
mydata=data.frame(x=rep(1:4,2),y=rep(1:2,each=4),z=c(1,2,3,4,4,3,2,1))
cloud(z~x*y,data=mydata,groups=y,type=rep("l",2))

Now, I would like to change the color of the lines (still works fine):

cloud(z~x*y,data=mydata,groups=y,type=rep("l",2),col=c(1,2))

But when I change the color to be the same for each group, i.e. for  
both lines, then the groups are "combined" by a line:

cloud(z~x*y,data=mydata,groups=y,type=rep("l",2),col=c(2,2))

How do I remove this group-combining line so that the cloud()-plot  
looks like in the first plot above, but with the same colors for each  
line? Assigning the color in the data.frame mydata also did not help.

Thanks!

marius