We would like to find a function which fits the 21 data
 points.  One way to do this is with a radial basis 
 network.  A radial basis network is a network with two 
 layers.  A hidden layer of radial basis neurons and an
 output layer of linear neurons.  Here is the radial basis
 transfer function used by the hidden layer:

 >> p =-3:.1:3;
 >> a = radbas(p);
 >> plot(p,a)