R help - Jun 2004 - contour lines on levelplot?

With "image" and "contour", one can get both colors and
lines to
enhance the image of a contour plot.  What's the best way to do this 
with Lattice graphics?  The following is one ugly hack, producing the 
desired result after much trial and error (R 1.9.1 alpha under Windows 
2000): 

# setup
DF <- expand.grid(x=1:3, y=1:3)
DF$z <- (DF$x+DF$y)

# Traditional "base" graphics: 
image(x=1:3, y=1:3, z=array(DF$z, dim=c(3,3)))
contour(x=1:3, y=1:3, z=array(DF$z, dim=c(3,3)), add=T)

# Lattice hack: 
lvlplt <- levelplot(z~x*y, DF)
cont <- contourplot(z~x*y, DF)
print(lvlplt, more=T)
print(cont, position=c(0, 0, 0.9055, 1))

##################
      By comparison, the same ugly hack in S-Plus required 0.952 instead 
of 0.955.  Is this the best we can currently get with a modest effort? 

      Thanks,
      spencer graves

On Sunday 06 June 2004 20:40, Spencer Graves wrote:
>       With "image" and "contour", one can get both
colors and lines
> to enhance the image of a contour plot.  What's the best way to do
> this with Lattice graphics?  The following is one ugly hack,
> producing the desired result after much trial and error (R 1.9.1
> alpha under Windows 2000):
>
> # setup
> DF <- expand.grid(x=1:3, y=1:3)
> DF$z <- (DF$x+DF$y)
>
> # Traditional "base" graphics:
> image(x=1:3, y=1:3, z=array(DF$z, dim=c(3,3)))
> contour(x=1:3, y=1:3, z=array(DF$z, dim=c(3,3)), add=T)
>
> # Lattice hack:
> lvlplt <- levelplot(z~x*y, DF)
> cont <- contourplot(z~x*y, DF)
> print(lvlplt, more=T)
> print(cont, position=c(0, 0, 0.9055, 1))
>
> ##################
>       By comparison, the same ugly hack in S-Plus required 0.952
> instead of 0.955.  Is this the best we can currently get with a
> modest effort?
There's certainly much easier ways to do this, namely 

contourplot(z~x*y, DF, region = TRUE)

or 

levelplot(z~x*y, DF, contour = TRUE)

the only restriction being that you would need to use the same 'at' 
vector. If you want them to differ, you need to write a small panel 
function of your own that makes use of panel.levelplot().

Deepayan