Matlab实现——to find the fixed point

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fixpt.m

 

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

% Input - g is the iteration function input as a string ??g??

%           - 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}

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

程序示例：

fun.m

 

function g=fun(x)

g=x^5-3*x^3-2*x^2+2;

Untitled3.m

p0=-1.6;

tol=10e-12;

max1=7;

g='fun';

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

运行的结果说明在点(-1.6,-1.8)附近的不动点是排斥不动点

 

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