抛物线代码matlab

以下是抛物线法的Matlab代码示例：

function x = parabolic(f, a, b, tol)
% f: 目标函数
% a, b: 初始搜索区间
% tol: 精度要求

% 初始化
x1 = a;
x2 = (a + b) / 2;
x3 = b;
f1 = f(x1);
f2 = f(x2);
f3 = f(x3);

% 迭代
while abs(x3 - x1) > tol
    A = ((f2 - f1) * (x3 - x2) - (f3 - f2) * (x2 - x1)) / ((x3 - x2) * (x2 - x1) * (x3 - x1));
    B = ((f3 - f2) * (x2 - x1) - (f2 - f1) * (x3 - x2)) / ((x3 - x2) * (x2 - x1) * (x3 - x1));
    x = (x1 + x2 - B / (2 * A)) / 2;
    fx = f(x);
    if x < x2
        if fx < f2
            x3 = x2;
            f3 = f2;
            x2 = x;
            f2 = fx;
        else
            x1 = x;
            f1 = fx;
        end
    else
        if fx < f2
            x1 = x2;
            f1 = f2;
            x2 = x;
            f2 = fx;
        else
            x3 = x;
            f3 = fx;
        end
    end
end
end