problem2.m

一个比较简单的模式识别问题。用female.txt 和male.txt 的数据作为训练样本集

female = dlmread('female.txt');
female=female(:,1:2);
male   = dlmread('male.txt');
male= male(:,1:2);
set    = dlmread('set3.txt');
favg = mean(female);
fsig = cov(female);

mavg = mean(male);
msig = cov(male);
msig(1,2)=msig(2,1)=0;
fsig(1,2)=fsig(2,1)=0;
[length,width] = size(set);
ma = 0.5;
fe = 0.5;
error1 = 0;
error2 = 0;
for i = 1:length
    Px = mvnpdf(set(i,1:2) ,favg,fsig)*fe + mvnpdf(set(i,1:2),mavg,msig)*ma;
    Pm = mvnpdf(set(i,1:2),mavg,msig)*ma/Px;
    Pf = mvnpdf(set(i,1:2),favg,fsig)*fe/Px;
    if Pm > Pf
        if set(i,3) ==2
            error1 = error1 + 1;
        end
    else
        if set(i,3) ==1
            error2 = error2 + 1;
        end
    end
end
errorratio = (error1+error2)/length