There is no easy way to do this. This essentailly amounts to surface fitting as opposed to curve fitting. I have spent weeks trying to figure out how to do 2D non linear Lev Mar. It was complicated and I hadto give up. The best recomendation I can offer is to surf the web. I found one link that I thought was particularlly good:
http://www.siggraph.org/education/materials/HyperVis/vistech/volume/surface1.htm
