机器学习及其matlab实现—从基础到实践——HW3

Contents

• I. 清空环境变量
• II. 训练集/测试集产生
• III. 数据归一化
• IV. BP神经网络创建、训练及仿真测试
• V. 性能评价
• VI. 画图

I. 清空环境变量

clear all
clc

II. 训练集/测试集产生

1. 导入数据

load concrete_data.mat

2. 随机产生训练集和测试集

temp = randperm(size(attributes,2));
% 训练集——80个样本
P_train = attributes(:,temp(1:80));
T_train = strength(:,temp(1:80));
% 测试集——23个样本
P_test = attributes(:,temp(81:end));
T_test = strength(:,temp(81:end));
N = size(P_test,2);

III. 数据归一化

[p_train, ps_input] = mapminmax(P_train,0,1);
p_test = mapminmax(‘apply‘,P_test,ps_input);

[t_train,ps_output] = mapminmax(T_train,0,1);

IV. BP神经网络创建、训练及仿真测试

1. 创建网络

net = newff(p_train,t_train,11);

2. 设置训练参数

net.trainParam.epochs = 1000;
net.trainParam.goal = 1e-3;
net.trainParam.lr = 0.01;

3. 训练网络

net = train(net,p_train,t_train);

4. 仿真测试

t_sim = sim(net,p_test);

5. 数据反归一化

T_sim = mapminmax(‘reverse‘,t_sim,ps_output);

V. 性能评价

1. 绝对误差error

error = abs(T_sim - T_test)./T_test;

2. 决定系数R^2

R2 = (N * sum(T_sim .* T_test) - sum(T_sim) * sum(T_test))^2 / ((N * sum((T_sim).^2) - (sum(T_sim))^2) * (N * sum((T_test).^2) - (sum(T_test))^2));

3. 结果对比

result = [T_test‘ T_sim‘ error‘]

result =

   28.1600   31.1291    0.1054
   52.6500   53.0643    0.0079
   30.9700   26.2469    0.1525
   38.4600   38.0986    0.0094
   41.1400   39.8364    0.0317
   30.8300   30.8207    0.0003
   36.1900   35.7525    0.0121
   32.7100   33.8095    0.0336
   41.0100   40.0879    0.0225
   32.8400   33.3301    0.0149
   33.9100   31.6726    0.0660
   38.1900   38.3960    0.0054
   26.4200   27.5678    0.0434
   17.1900   18.4602    0.0739
   35.5200   35.2201    0.0084
   49.9700   51.0821    0.0223
   48.7700   48.8715    0.0021
   46.3600   46.2920    0.0015
   31.5000   29.0295    0.0784
   42.0800   42.0742    0.0001
   36.4600   39.2970    0.0778
   44.4800   44.6282    0.0033
   58.5300   53.3348    0.0888

VI. 画图

figure
plot(1:N,T_test,‘b:*‘,1:N,T_sim,‘r-o‘)
legend(‘真实值‘,‘预测值‘)
xlabel(‘预测样本‘)
ylabel(‘混凝土抗压强度‘)
string = {‘测试集混凝土抗压强度预测结果对比‘;[‘R^2=‘ num2str(R2)]};
title(string)

Published with MATLAB? R2015a

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