error in nonlinear system

please ! can you detect the errors of this code? and how i can get the answer correctly!

fun = @(x) [x(1) ^ 2 + x(2) ^ 2 + x(3) ^ 2 - 1; ...
            x(1) ^ 2 + x(3) ^ 2 - 0.25; ...
            x(1) ^ 2 + x(2) ^ 2 + 4 * x(3)];

J = @(x) [ 2 * x(1) + 2 * x(2)  + 2 * x(3)  ; ...
            2 * x(1)  + 2 * x(3);  ...
            2 * x(1)  + 2 * x(2)  - 4 ];

x0 = [1;1;1]'; tol= 0.00001;  maxit= 10;
xold = x0; iter=1; 

while (iter<= maxit) 
    y= -feval(J,xold)\ feval(f,xold);
    xnew=xold + y';
    dif = norm(xnew-xold);
    disp(iter);   disp(xnew);    disp(dif); 

    if dif <= tol 
        x=xnew ; 
        disp (' Newton method has converged '), return;
    else
        xold= xnew;
    end 
    iter = iter + 1;
    disp(' itre                  xnew                  dif')
end 

disp('Newton method did not converge')
x = xnew ;

Answer 1

[Torsten]

Why is your Jacobian (3x1) and not (3x3) ?

And replace

y = -feval(J,xold)\ feval(f,xold);

by

y = -J(xold)\fun(xold)

Best wishes

Torsten.

[king skiler]

still not working , because adding matrix wrong in the line of : xnew=xold+y;

[Torsten]

For me, it works:

fun = @(x) [x(1) ^ 2 + x(2) ^ 2 + x(3) ^ 2 - 1; ...
            x(1) ^ 2 + x(3) ^ 2 - 0.25; ...
            x(1) ^ 2 + x(2) ^ 2 + 4 * x(3)];

J = @(x) [ 2 * x(1) , 2 * x(2)  , 2 * x(3)  ; ...
            2 * x(1),0,   2 * x(3);  ...
            2 * x(1)  , 2 * x(2),  4 ];

x0 = [1;1;1]'; tol= 0.00001;  maxit= 100;
xold = x0; iter=1; 

while (iter<= maxit) 
    y= -J(xold)\ fun(xold);
    xnew=xold + y';
    dif = norm(xnew-xold);
    disp(iter);   disp(xnew);    disp(dif); 

      if dif <= tol 
          x=xnew ; 
          disp (' Newton method has converged '), return;
      else
          xold= xnew;
      end 
      iter = iter + 1;
      disp(' itre                  xnew                  dif')
  end 
  disp('Newton method did not converge')
  x = xnew ;