fixpt.m

国外计算机科学教材系列 numerial method using matlab (third edition)

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) 1999 by John H. Mathews and Kurtis D. Fink
%To accompany the textbook:
%NUMERICAL METHODS Using MATLAB,
%by John H. Mathews and Kurtis D. Fink
%ISBN 0-13-270042-5, (c) 1999
%PRENTICE HALL, INC.
%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';