deycjz_mid.m

人工免疫是对生物免疫系统的工作机理及所具有各种优良特性的模拟。在邮件系统中 引入免疫的思想,构建了一种基于人工免疫的反垃圾邮件模型。

function y = DEYCJZ_mid(f, h,a,b,y0,varvec,type,s)
format long;
N = (b-a)/h;
y = zeros(N+1,1);
x = a:h:b;
y(1) = y0;
y(2) = y0+h*Funval(f,varvec,[x(1) y(1)]);
var = findsym(f);
if type == 1
    for i=3:N+1
        v1 = Funval(f,varvec,[x(i-1) y(i-1)]);
        t = y(i-2) + 2*h*v1;
        v2 = Funval(f,varvec,[x(i) t]);
        y(i) = y(i-1)+h*(v1+v2)/2;
    end
else
    if type == 2
        for i=3:N+1
            v1 = Funval(f,varvec,[x(i-1) y(i-1)]);                
            t = y(i-2) + 2*h*v1;
            v2 = Funval(f,varvec,[x(i) t]);
            for l=1:s
                y(i) = y(i-1)+h*(v2 + v1)/2;
                v2 = Funval(f,varvec,[x(i) y(i)]);
            end
        end
    else
        p0 = 0;
        c = 0;
        fnl = Funval(f,varvec,[x(1) y(1)]);
        for i = 3:N+1
            v1 = Funval(f,varvec,[x(i-1) y(i-1)]);
            p = y(i-2)+2*h*v1;
            M = p - 0.8*(p0 - c);
            F = Funval(f , varvec, [x(i) ,M]);
            fn = y(i-1) + h*(fnl + F)/2;
            y(i) = fn - 0.2*( p - fn);
            c = fn;
            fnl = fn;
            p0 = p;
        end
    end
end
format short;