clear all
sprintf('hello\n');

% ask for terminating time
endTime = input('Simulate the Initial Value Problem from time 0 until?: ');

% initial conditions
time(1) = 0.0;
v(1) = 0;
s(1) = 0;
sp_weight = 70;

% constants, Cd is changed to make it same as the coefficient in ODE lecture!
g = 9.8;
Cd = 10;
delta_t = 0.5;

% start time/index
t = 0.0;
i = 2;

% the main program
while (t < endTime)
  % update time
  t = t + delta_t;
  time(i) = t;

  % compute velocity v(i)
  v(i) = v(i-1) + (g * sp_weight - Cd * v(i-1)) / sp_weight * delta_t;

  % compute distance traveled in m
  s(i) = s(i-1) + v(i) * delta_t;

  % update i
  i = i+1;
end % while

% output the results side by side
% spidey position versus time
subplot(2,1,1);
plot(time, s);
xlabel('Time (s)');
ylabel('S (m)');
title('Spidey''s Position versus Time');

% spidey velocity versus time
subplot(2,1,2);
plot(time, v);
xlabel('Time (s)');
ylabel('Velocity (m/s)');
title('Spidey''s Velocity versus Time');