bayesian.m

模式识别较全的讲解

function Bayesian_classify
%%%%%%两类正态模式的贝叶斯分类程序%%%%%%%%%
%输出：判别界面的表达式
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clc;
clear;
w1 = [0 2 2 0;    %待分类的模式
      0 0 2 2];
w2 = [4 6 6 4;
      4 4 6 6];
Pw1 = 1/2;
Pw2 = 1/2;
num1 = size(w1,2);
num2 = size(w2,2);
m1 = mean(w1,2);
m2 = mean(w2,2);
C1 = zeros(2,2);
C2 = zeros(2,2);
for i=1:num1
    C1 = C1+w1(:,i)*w1(:,i)'-m1*m1';
end
C1 = C1/num1;
for i=1:num2
    C2 = C2+w2(:,i)*w2(:,i)'-m2*m2';
end
C2 = C2/num2;

x1 = sym('x1','real');
x2 = sym('x2','real');
x = [x1;x2];
d1 = log(Pw1)-1/2*log(det(C1))-1/2*(x-m1)'*inv(C1)*(x-m1);
d2 = log(Pw2)-1/2*log(det(C2))-1/2*(x-m2)'*inv(C2)*(x-m2);
fprintf('判别界面的表达式为：\n');
d12 = simplify(d1-d2)