newton_raphson.m

来自「Newton-Raphson numerical method」· M 代码 · 共 32 行

clear all;
clc;

%===============================
% % Newton method with numerical derivative
% clear all;
% clc;
% 
% 
% f=input('f(x)=','s');
% tol=input('error tolerance =1e-5, new tolerance=');
% if length(tol)==0,tol=1e-5;end
% x1=input(' First guess=');
% x=x1; fx=eval(f);
% for i=1:100
%   if abs(fx)<tol, break,end
%   x=x+.01;
%   ff=eval(f);
%   fdx=(ff-fx)/.01;
%   x1=x1-fx/fdx;
%   x=x1;
%   fx=eval(f);
%   fprintf('i = %g, x = %g, fx = %g\n',i,x,fx)
% end
% 
% % f(x)=x^3+4*x^2-10
% % error tolerance =1e-5, new tolerance=
% %  First guess=1.5
% % i = 1, x = 1.37391, fx = 0.143874
% % i = 2, x = 1.36531, fx = 0.00129871
% % i = 3, x = 1.36523, fx = 6.39291e-006