[R] Contour plot for arbitrary (x,y,z)

[Ronnen Levinson]

Hello.

Is there an easy-to-use contour plot function analogous to scatterplot3d 
that can draw handle a dataset of arbitrary (x,y,z) triplets? That is, 
say x, y, and z are each measured quanties, and exhibit neither order 
nor regularity.

I looked at the lattice package function "contourplot" but it seems 
complicated, and it's not clear from the documentation whether it can 
handle arbitrary (x,y) values. I'm looking for something like the base 
package "contour" function that does not make any assumptions about (x,y,z).

Thanks,

Ronnen.