How can i correct Newton rhapson method??

In Newton rhapson method ,i try to solve nonlinear equation . I think below cod is right. but values are not shown .

i don't understand why the result show just '120' as value. x f(x) 120.000000, 48.000000 x f(x) 102.000000, 120.000000 what's the error in below ???

please~~

thanks for your help

end
f=inline('exp(-x)-x','x');
df=inline('-exp(-x)-1','x');
epsilon=0.0001;
imax=1000;
x0=input('initial xo=');
fx0=f(x0);
  if abs(fx0)<=epsilon
      fprintf('xo is value');
      return;
  end
  if abs(df(x0))<=epsilon
      fprintf('input another xo');
      return;
  end
  for iter=1:imax
      x0=x0-fx0/df(x0);
      fx0=f(x0);
      fprintf('\n x  f(x)  %f,  %f','x0','fx0');
      if abs(fx0)<=epsilon
           fprintf('\n value x= %f','x0');
           return;
      end
  end

Answer 1

[Pourya Alinezhad]

you may use somthing like this :

while abs(xold -xnew) > tol
xold = xnew;
xnew = xold - feval(f,xold)/feval(fprime,old);
end
out = xnew;

delete the "for" loop and use a while command instead.

Answer 2

[Pourya Alinezhad]

the algorithm should be like this pseudo code...

function out = Newton(f,fprime,xstart,tol)
xold = xstart;
xnew = xold - feval(f, xold)/feval(fprime,xold);
while abs(xold -xnew) > tol
xold = xnew;
xnew = xold - feval(f,xold)/feval(fprime,old);
end
out = xnew;