secant.m

优化设计中的一维搜索方法

function [fx,fy,iter] = secant(func,limt)
if length(limt)~=2
    error('error input limt!');
end
%falpha1 = subs(func,limt(1));
fdalpha1 = subs(diff(func),limt(1));
fdalpha2 = subs(diff(func),limt(2));
newp = limt(1) - ((limt(1)-limt(2))*fdalpha1)/(fdalpha1-fdalpha2);
fdnewp = subs(diff(func),newp);
iter = 0;
while abs(fdnewp)>10^10*eps
    if fdnewp<0
        limt(1) = newp;
    else
        limt(2) = newp;
    end
    fdalpha1 = subs(diff(func),limt(1));
    fdalpha2 = subs(diff(func),limt(2));
    newp = limt(1) - ((limt(1)-limt(2))*fdalpha1)/(fdalpha1-fdalpha2);
    fdnewp = subs(diff(func),newp);
    iter = iter+1;
    end
fx = newp;
fy = subs(func,newp);