Update values in while loop and store values from a while loop in arrays

Hi I am trying to run a while loop to calculate the error values. I am struggling to update the values in the while loop and then store them all. I need to store the number of iterations and all the error values per iteration while update the value of x_old to call my function again. I have my code posted below, but I can't get my values to update. Any helo would be appreciated.

% Exercise 2.1 Order of Convergence

clear
close
clc

% Define Variables
F = 12;
x_old = 0;
itr = 0;
epsilon_new = 1e30;
epsilon_target = 1e-6;


while epsilon_new > epsilon_target
    itr = itr+1;
   
    [x_new] = springcalc(F, x_old);
    epsilon_new = abs(x_new - x_old);
    eps_matrix = [epsilon_new];
    x_old = x_new;  
end

semilogy(itr, epsilon_matrix);

function [x_new] = springcalc(F, x_old)
k_0 = 30;
x_new = F/(k_0*(1+x_old^(0.1)));
end

Answer 1

[David Hill]

% Exercise 2.1 Order of Convergence
clear
close
clc
% Define Variables
F = 12;
x_old = 0;
itr = 0;
epsilon_new = 1e30;
epsilon_target = 1e-6;
while epsilon_new > epsilon_target
    itr = itr+1;
   
    x_new = springcalc(F, x_old);
    epsilon_new = abs(x_new - x_old);
    epsilon(itr)=epsilon_new;
    x_old = x_new;  
end
semilogy(1:length(epsilon), epsilon);

function [x_new] = springcalc(F, x_old)
k_0 = 30;
x_new = F/(k_0*(1+x_old^(0.1)));
end

[Nnamdi Chukwunenye]

Hey David thanks for the help. just wanted to note that epsilon was misspelled a couple of times for anyone who uses this solution inthe future.

[David Hill]

Sorry, fixed.

[Neeraj Kumar]

David, will you help me this issue-

https://in.mathworks.com/matlabcentral/answers/594451-how-to-store-a-matrix-a-in-variable-x-where-x-is-also-carrying-a-counter-i