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Highlights from
Numerical Methods Using MATLAB, 3e

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Numerical Methods Using MATLAB, 3e

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20 Aug 2002 (Updated )

Companion Software

[p1,err,k,y]=secant(f,p0,p1,delta,epsilon,max1)
function [p1,err,k,y]=secant(f,p0,p1,delta,epsilon,max1)

%Input - f is the object function input as a string 'f'
%      - p0 and p1 are the initial approximations to a zero of f        
%	    - delta is the tolerance for p1
%	    - epsilon is the tolerance for the function values y
%	    - max1 is the maximum number of iterations
%Output - p1 is the secant method approximation to the zero
%	     - err is the error estimate for p1
%	     - k is the number of iterations
%	     - y is the function value f(p1)

% 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

for k=1:max1	
	p2=p1-feval(f,p1)*(p1-p0)/(feval(f,p1)-feval(f,p0));	
	err=abs(p2-p1);
	relerr=2*err/(abs(p2)+delta);
	p0=p1;
	p1=p2;
	y=feval(f,p1);
	if (err<delta)|(relerr<delta)|(abs(y)<epsilon),break,end
end

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