Fixed point (matematice)

Hello.

I have attempt to code a fixed point in MATLAB. But I don't know if this correct, but I think it works.

 function sol=fixpunkt(g,x0,tol) 

xnew=x0; 
xold=x0+2*tol; 

while norm(xold-xnew)>tol 

        xnew  =  xnew     

      xnew=g(x0) ;   
  end
  sol=xnew;

When I tried fixpunkt(1,1,5) in the command window, MATLAB works 'busy' for a long long time, I guess it is the while loop doing that,

I would be happy if someone can give a opinion about this.

Regards Cillian

Answer 1

[Richard Brown]

xold never gets updated, so xnew gets set to the same value every iteration, and the loop never ends ...

Answer 2

[Titus Edelhofer]

Hi,

and in addition to Richards observation: it's always not a bad idea to do something like

iter = 0;
maxIter = 50;
while norm(xold-xnew)>tol && iter<maxIter
  % do fix point iteration here,
  % then:
  iter = iter + 1;
end