f最速下降法.m

来自「最优化算法」· M 代码 · 共 35 行

function y=F(x)
y=(x(1)-15)^2+(x(2)-45)^4;

function y=D_F(x)
%D_F Summary of this function goes here
%  Detailed explanation goes here
y=[0,0];
y1=2*(x(1)-15),  y2=4*((x(2)-45)^3);
y=[y1,y2];


format long
x=[0,0];
x=input('请输入初始值[x0,x1]=',[0,0]);
s=input('请输入初始精度s＝',0.1);
g=D_F(x);
g=g.';%转置为列向量；
while(norm(g)>s) 
    s_k=-g,   r=min_F(x,s_k),   x=x+r.*s_k.';
    g=D_F(x);
    g=g.';
 fprintf('The result is %8.5f\n', x); 
    fprintf('The daosu is %8.5f\n', g);   
end
axis normal;
hold on;
view([1,1,1]);
for i=-100:100
   for j=-100:100
z=[i,j],  z=F(z);
plot3(i,j,z);
end
end
hold off;