R help - Jun 2008 - re-arranging unsorted data for surface/contour plot

Hi list,

I'm struggling with plotting a 3d data set.

I have a data frame with x,y and z values. They occur in no particular order (ie
x and y are not ordered).

However, I want to visualize the data using a contour plot.

Now, the x,y and z data going into contour() are supposed to be ordered. 

My question is: Is their a quick way to re-arrange my data such that it can be
fed to contour()?

I know about interp(). However, using this, I found some strange quirks in the
interpolation that I would rather not see (both linair and non linear
interpolation).

I have plotted my data with plot3d() in the RGL package. This works fine. But I
need a 2d plot (x~y projection). Maybe I can color the plot3d() plot and use a
projected version?

Any ideas are welcome,

Regards,
Dieter