[R] Persp plotting of kernel density estimate.

[C Peroni]

Dear All, 

I am trying to visualize the surface of a bivariate kernel density
estimate. 
I have a vector of bivariate observations(x,y), and a function which
computes the kernel density estimate z corresponding to each
observation. I cannot generate the (x,y) data in the ascending order
needed by persp(x,y,z). 
I was wondering whether there is an R version of the S function interp.

Would anybody be able to help.
Thank you in advance.

Chiara