[R] density plot - beginner's question

[Saurav Pathak]

Hi,

I am trying to plot densities given on a two dimensional grid.  My
data is in the an external file, and is arranged in three columns:
x, y, density

how may i get a plot of this?  i would like to get (1) a three
dimensional plot and (2) a color coded two dimensional plot.

I have tried using 

	image(x, y, density)

but i am asked to put the data in ascending order.  i am not sure
how i may put grid points in an ascending order.

I would also like to know if i could use any other function, other
than image.

thank you in advance.

-- 
saurav