demorb4.m

神经网络学习过程的实例程序

%% Radial Basis Overlapping Neurons
% A radial basis network is trained to respond to specific inputs with target
% outputs.  However, because the spread of the radial basis neurons is too high,
% each neuron responds essentially the same, and the network cannot be designed.
% 
% Copyright 1992-2002 The MathWorks, Inc.
% $Revision: 1.16 $  $Date: 2002/04/14 21:28:23 $

%%
% Define 21 inputs P and associated targets T.

P = -1:.1:1;
T = [-.9602 -.5770 -.0729  .3771  .6405  .6600  .4609 ...
      .1336 -.2013 -.4344 -.5000 -.3930 -.1647  .0988 ...
      .3072  .3960  .3449  .1816 -.0312 -.2189 -.3201];
plot(P,T,'+');
title('Training Vectors');
xlabel('Input Vector P');
ylabel('Target Vector T');

%%
% The function NEWRB quickly creates a radial basis network which approximates
% the function defined by P and T.
% 
% In addition to the training set and targets, NEWRB takes two arguments, the 
% sum-squared error goal and the spread constant.  The spread of the radial
% basis neurons B is set to a very large number.

eg = 0.02; % sum-squared error goal
sc = 100;  % spread constant
net = newrb(P,T,eg,sc);

%%
% NEWRB cannot properly design a radial basis network due to the large overlap
% of the input regions of the radial basis neurons.  All the neurons always
% output 1, and so cannot be used to generate different responses.  To see how
% the network performs with the training set, simulate the network with the
% original inputs.  Plot the results on the same graph as the training set.

Y = sim(net,P);
hold on;
plot(P,Y);
hold off;