matlab实现二元函数BP网络,m文件实现bp神经网络逼近二元函数

clc

clear

close all

x1=-1:0.01:1;                               %生成训练数据x

x2=-1:0.01:1;

[X1,X2]=meshgrid(x1,x2);

yd=sin(pi*X1).*cos(pi*X2);

figure;

mesh(X1,X2,yd);

title('标准sin(pi*x1)*cos(pi*x2)图像');

hold on;

Input=2;

HideLayer=5;

Output=1;

%权值及阈值初始化

w1=rands(HideLayer,Input);%隐含层的权值和阈值

b1=rands(HideLayer,1);

w2=rands(Output,HideLayer);%输出层的权值和阈值

b2=rands(Output,1);

% dw1=zeros(HideLayer,Input);

% dw2=zeros(Output,HideLayer);

error = 0.01;%误差阈值

xite=0.3;         %学习速率

M=201;

for m1=1:M

for m2=1:M

y=sin(pi*x1(m1))*cos(pi*x2(m2));

for k=1:50

for i=1:HideLayer%隐层的输出

HOut(i)=logsig(x1(m1)*w1(i,1)+x2(m2