Having issue with this secant method code

It's having an issue with the second line when it asks to enter the function. any help appreciated

clear all; close all;
a=input('What is the function?  ' );
f=inline(a)
x(1)=input('What is your first guess? ');
x(2)=input('What is your second guess? ');
tol=input('What is the tolerance? ');
iteration=0;
i=2;
eps = 1e10;

while (abs(eps) > tol)
  x(i+1)=x(i)-f(x(i))*(x(i)-x(i-1))/(f(x(i))-f(x(i-1)));
  eps = x(i+1)-x(i);
  i = i+1;
  x(i)
end