Not enough input agruments

% Set the circuit parameters and initial conditions
res = 10 * 9;
C = 0.0001/9;
L = 0.01 * 4;
V0 = 0;
I = 1;
omega = 2 * pi * 0;
I0 = [1; 0];
% Solve the system using ode45()
[t_ode45, I_ode45] = ode45(@(t, I) Question3(t, I, res, L, C, V0, omega), [0, 40 * L / res], I0);
% Set the time step and the number of time steps
h = 0.001;
N = ceil(40 * L / res / h);
% Use the forward Euler method to solve the system
t_euler = zeros(N, 1);
I_euler = zeros(N, 2);
I_euler(1, :) = I0;
for n = 1:N-1
    t_euler(n+1) = t_euler(n) + h;
    I_euler(n+1, :) = I_euler(n, :) + h * Question3(t_euler(n), I_euler(n, :), res, L, C, V0, omega)';
end
% Use the backward Euler method to solve the system
t_beuler = zeros(N, 1);
I_beuler = zeros(N, 2);
I_beuler(1, :) = I0;
for n = 1:N-1
    t_beuler(n+1) = t_beuler(n) + h;
    f = @(I) I - I_beuler(n, :) - h * Question3(t_beuler(n+1), I, res, L, C, V0, omega)';
    I_beuler(n+1, :) = fsolve(f, I_beuler(n, :));
end

Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.

% Plot the results
figure;
plot(t_ode45, I_ode45(:, 1), 'b-', 'LineWidth', 1.5);
hold on;
plot(t_euler, I_euler(:, 1), 'r--', 'LineWidth', 1.5);
plot(t_beuler, I_beuler(:, 1), 'm-.', 'LineWidth', 1.5);
xlabel('Time (s)');
ylabel('Current (A)');
title('RLC Circuit in Series');
legend('ode45', 'Forward Euler', 'Backward Euler');

% Define the function for the RLC circuit in series
function dIdt = Question3(t, I, res, L, C, V0, omega)
dIdt = [I(2); (V0 * omega * cos(omega * t) - res * (I(2) - I(1)) / C) / L];  
end

[Torsten]

I don't know how you got this problem - your code works (at least no syntax errors).

Answer 1

[Chunru]

Function should be placed at the end of script or separate file:

% Set the circuit parameters and initial conditions
res = 10 * 9;
C = 0.0001/9;
L = 0.01 * 4;
V0 = 0;
I = 1;
omega = 2 * pi * 0;
I0 = [1; 0];
% Solve the system using ode45()
[t_ode45, I_ode45] = ode45(@(t, I) Question3(t, I, res, L, C, V0, omega), [0, 40 * L / res], I0);
% Set the time step and the number of time steps
h = 0.001;
N = ceil(40 * L / res / h);
% Use the forward Euler method to solve the system
t_euler = zeros(N, 1);
I_euler = zeros(N, 2);
I_euler(1, :) = I0;
for n = 1:N-1
    t_euler(n+1) = t_euler(n) + h;
    I_euler(n+1, :) = I_euler(n, :) + h * Question3(t_euler(n), I_euler(n, :), res, L, C, V0, omega)';
end
% Use the backward Euler method to solve the system
  t_beuler = zeros(N, 1);
 I_beuler = zeros(N, 2);
 I_beuler(1, :) = I0;
 for n = 1:N-1
    t_beuler(n+1) = t_beuler(n) + h;
    f = @(I) I - I_beuler(n, :) - h * Question3(t_beuler(n+1), I, res, L, C, V0, omega)';
    I_beuler(n+1, :) = fsolve(f, I_beuler(n, :));
 end

Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.


Equation solved, solver stalled.

fsolve stopped because the relative size of the current step is less than the
value of the step size tolerance squared and the vector of function values
is near zero as measured by the value of the function tolerance.


Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the value
of the function tolerance. However, the last step was ineffective.

% Plot the results
 figure;
  plot(t_ode45, I_ode45(:, 1), 'b-', 'LineWidth', 1.5);
  hold on;
  plot(t_euler, I_euler(:, 1), 'r--', 'LineWidth', 1.5);
  plot(t_beuler, I_beuler(:, 1), 'm-.', 'LineWidth', 1.5);
  xlabel('Time (s)');
  ylabel('Current (A)');
  title('RLC Circuit in Series');
  legend('ode45', 'Forward Euler', 'Backward Euler');

  
  % Function should be placed at the end of script or separate file
  function dIdt = Question3(t, I, res, L, C, V0, omega)
  dIdt = [I(2); (V0 * omega * cos(omega * t) - res * (I(2) - I(1)) / C) / L];  
  end