How can I run this code for Fixed point iteration with given functions?

function x = FixedPtSys(G, x0, tol, maxit)

disp([0     x0]);       y = feval(G, x0);
xnew = y';      % the next solution
dif = norm(xnew - x0);
if dif <= tol
    x = xnew; return;
else
    xold = xnew;
end
disp( [1    xnew    dif ]);
iter = 2;
while (iter <= maxit)
    y = feval(G, xold);     xnew = y';      dif = norm(xnew - xold);
    if dif <= tol
        x = xnew;
        disp(' Fixed-point iteration converged'); return;
    else
        xold = xnew;
    end
    disp( [ iter    xnew    dif ]);
    iter = iter + 1;
end
disp(' Fixed-point iteration did not converge')
x = xold

Given functions:

f(x,y,z) = x^2 + 20x + y^2 + z^2 -20 = 0
g(x,y,z) = x^2 + 20Y + z^2 - 20 = 0
h(x,y,z) = x^2 + y^2 -40z = 0

Answer 1

[Walter Roberson]

funs = @(x,y,z) ...
  [x.^2 + 20*x + y.^2 + z.^2 - 20;
   x.^2 + 20*y + z.^2 - 20;
   x.^2 + y.^2 - 40*z];

FixedPtSys(@(xyz) funs(xyz(1), xyz(2), xyz(3), .......)

[SEUNGMYEONG CHOO]

please show me how you run the code.

[Walter Roberson]

 funs = @(x,y,z) ...
  [x.^2 + 20*x + y.^2 + z.^2 - 20;
   x.^2 + 20*y + z.^2 - 20;
   x.^2 + y.^2 - 40*z];

G = @(xyz) funs(xyz(1), xyz(2), xyz(3));

x0 = rand(1,3);
tol = 1e-8;
maxiter = 20;

x = FixedPtSys(G, x0, tol, maxiter);