I want to get the values from the last two iteration

Hi, i am creating a program, that follows the secant method, wherein you input two guesses which are xi1, xi and a error tolerance, the problem i have here is that i do not know how to replace the newxi as xi and the last xi from the iteration as xi1. In the image we can see that as iteration 3 and beyond is has the same values all the way since i do not know how to replace xi and xi1. by the way, xi at i=0 is the first guess while xi at i=1 is the xi1 or the second guess

disp('i         xi              f(xi)            ear')   %Header
for i=0:200
    if i==0
    xinew=xi1;                           %Calculate xi
    fxi=y(xinew);
    elseif i==1
        xinew=xi;
        fxi=y(xinew);
    elseif i>1
    xinew=xi-((y(xi)*(xi-xi1))/(y(xi)-y(xi1)));                           %Calculate xi
    fxi=y(xinew);
    end
    fprintf('%2.i %18.8f %15.8f \n',i,xinew,fxi)      %Creation of rows in the iteration

Answer 1

[Torsten]

 % Tolerances, Maximum number of iterations
  tolF = 1e-6;
  tolX = 1e-8;
  itermax = 30;
  % Start values
  xim2 = 6;
  xim1 = 4;
  fim2 = f(xim2);
  fim1 = f(xim1);
  % Initialization
  errorF = 1.0;
  errorX = 1.0;
  iter = 0;
  % Iteration loop
  while (errorF > tolF || errorX > tolX) && iter < itermax
    xi = xim1 - fim1*(xim1-xim2)/(fim1-fim2)
    fi = f(xi);
    errorF = abs(fi);
    errorX = abs(xi-xim1)
    fim2 = fim1;
    fim1 = fi;
    xim2 = xim1;
    xim1 = xi;
    iter = iter + 1;
  end
  % Result
  xi, fi

% Function definition
function y = f(x)
  y = (x-3).^2 - 4
end