demolin8.m

神经网络学习过程的实例程序

%% Adaptive Noise Cancellation
% A linear neuron is allowed to adapt so that given one signal, it can predict a
% second signal.
% 
% Copyright 1992-2002 The MathWorks, Inc.
% $Revision: 1.13 $  $Date: 2002/04/14 21:27:38 $

%%
% TIME defines the time steps of this simulation.  P defines a signal over these
% time steps.  T is a signal derived from P by shifting it to the left,
% multiplying it by 2 and adding it to itself.

time = 1:0.01:2.5;
X = sin(sin(time).*time*10);
P = con2seq(X);
T = con2seq(2*[0 X(1:(end-1))] + X);

%%
% Here is how the two signals are plotted:

plot(time,cat(2,P{:}),time,cat(2,T{:}),'--')
title('Input and Target Signals')
xlabel('Time')
legend({'Input','Target'})

%%
% The linear network must have tapped delay in order to learn the time-shifted
% correlation between P and T.  NEWLIN creates a linear layer.  [-3 3] is the
% expected input range.  The second argument is the number of neurons in the
% layer.  [0 1] specifies one input with no delay and one input with a delay of
% one.  The last argument is the learning rate.

net = newlin([-3 3],1,[0 1],0.1);

%%
% ADAPT simulates adaptive networks.  It takes a nework, a signal, and a target
% signal, and filters the signal adaptively.  Plot the the output Y in blue, the
% target T in red and the error E in green.  By t=2 the network has learned the
% relationship between the input and the target  and the error drops to near
% zero.

[net,Y,E,Pf]=adapt(net,P,T);
plot(time,cat(2,Y{:}),'b', ...
   time,cat(2,T{:}),'r', ...
   time,cat(2,E{:}),'g',[1 2.5],[0 0],'k')
legend({'Output','Target','Error'})