newton.m

来自「Nonlinear Problem Files Collection」· M 代码 · 共 49 行

function [] = newton(f,Df,x0,maxite);

format compact

xMax=1.5*abs(x0);
xMin=-xMax;

yMax=abs(feval(f,xMax));

t = xMin:0.05:xMax;
plot(t,feval(f,t),'k-');

axis([xMin xMax -yMax yMax]);

hold on;
plot([xMin xMax],[0 0],'k-');
hold on;
plot([0 0],[-yMax yMax],'k-');

x(1)=x0; k=1;
y(1)=0;
disp(sprintf('x_%d=%f',k-1,x(k)));


for k=2:2:2*maxite
   waitforbuttonpress;
   x(k)=x(k-1);
   y(k)=feval(f,x(k));

   dx=-feval(f,x(k))/feval(Df,x(k));
  
   x(k+1)=x(k)+dx;
   disp(sprintf('x_%d=%f',k/2,x(k+1)));
   y(k+1)=0;
   plot(x,y,'r*-');
 

end;


hold off;