运用BP进行非线性二分类,给出matlab代码
时间: 2023-11-07 16:44:57 浏览: 56
以下是一个基本的BP神经网络二分类器的matlab代码:
% 创建训练数据
X = [0 0 1 1; 0 1 0 1];
Y = [0 1 1 0];
% 设置神经网络参数
input_layer_size = 2;
hidden_layer_size = 4;
output_layer_size = 1;
alpha = 0.1;
num_iters = 10000;
% 初始化权重
theta1 = rand(hidden_layer_size, input_layer_size+1);
theta2 = rand(output_layer_size, hidden_layer_size+1);
% 添加偏置项
X = [ones(1,size(X,2));X];
% 训练神经网络
for i=1:num_iters
% 前向传播
a1 = X;
z2 = theta1*a1;
a2 = sigmoid(z2);
a2 = [ones(1,size(a2,2));a2];
z3 = theta2*a2;
a3 = sigmoid(z3);
% 计算误差
delta3 = a3-Y;
delta2 = (theta2(:,2:end)'*delta3).*sigmoidGradient(z2);
% 更新权重
theta2_grad = delta3*a2';
theta1_grad = delta2*a1';
theta2 = theta2-alpha*theta2_grad;
theta1 = theta1-alpha*theta1_grad;
end
% 预测
test = [0 0; 0 1; 1 0; 1 1];
test = [ones(1,size(test,2));test];
a2 = sigmoid(theta1*test);
a2 = [ones(1,size(a2,2));a2];
a3 = sigmoid(theta2*a2);
disp(a3>0.5);
% sigmoid函数
function g = sigmoid(z)
g = 1./(1+exp(-z));
end
% sigmoid函数的导数
function g = sigmoidGradient(z)
g = sigmoid(z).*(1-sigmoid(z));
end
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