derivatives in R

Hi, I posted this message earlier in "Rmetrics" and I don't know
whether I posted in the wrong place, so I'm posting it again in
Rhelp. 

I have a function in x and y and let's call it f(x,y). I need to get
the Hessian matrix. i.e I need (d^2f/dx^2), (d^2f/dxdy),
(d^2f/dydx), (d^2f/dy^2).I can get these using the D function. now I
need to evaluste the hessian matrix for -5<x<5 and -2<y<2 and I also
need to print the output. 

I tried  using a for loop,but it is giving me an error.