fixpt.m

提供一个直接搜索算法程序

function [k,p,err,P] = fixpt(g,p0,tol,max1)

% Input - g is the iteration function 
%       - p0 is the initial guess for the fixed-point
%       - tol is the tolerance
%       - max1 is the maximum number of iterations 
% Output - k is the number of iterations that were carried out
%	      - p is the approximation to the fixed-point
%	      - err is the error in the approximation
%	      - P'contains the sequence {pn}

%  NUMERICAL METHODS: Matlab Programs
% (c) 2004 by John H. Mathews and Kurtis D. Fink
%  Complementary Software to accompany the textbook:
%  NUMERICAL METHODS: Using Matlab, Fourth Edition
%  ISBN: 0-13-065248-2
%  Prentice-Hall Pub. Inc.
%  One Lake Street
%  Upper Saddle River, NJ 07458

P(1)= p0;
for k=2:max1
	P(k)=feval(g,P(k-1));
	err=abs(P(k)-P(k-1));
	relerr=err/(abs(P(k))+eps);
	p=P(k);
	if (err<tol) | (relerr<tol),break;end
end

if k == max1
	disp('maximum number of iterations exceeded')
end

P=P';