Here are three two-element input vectors, P, and their 
associated classes, Tc.  We would like to create a 
probabilistic neural network that classifies these vectors
properly.

>> P = [1 2; 2 2; 1 1]';
>> Tc = [1 2 3];
>> plot(P(1,:),P(2,:),'.','markersize',30)
>> for i=1:3,
>>   text(P(1,i)+0.1,P(2,i),sprintf('class %g',Tc(i)))
>> end
>> axis([0 3 0 3])