MATLAB: Not enough input arguments, ODE 45, System of ODEs

odeode45

Hello everybody! I seem to be very unlucky, I can not find any solution to my problem – I have:
Error using chu2 (line 9)
Not enough input arguments.
Here is my code:
      function dy = chu2(y)
      m0 = -3/7;
      m1 = 4/7;
      alpha = 9;
      beta = 14;
      dy = zeros(3,1);
      dy(1) = alpha*(y(2) - y(1) - (.5)*(m0 - m1)*(abs(y(1) + 1) - abs(y(1) - 1)));
      dy(2) = y(1) - y(2) + y(3);
      dy(3) = -beta*y(2); 
      [~,Y] = ode45(@chu2,[0 1 1]);
      plot3(Y)
Firstly, I thought the problem is because I gave not enough info, but I have checked everything.
Also I have a question about ODE45 – what method Matlab uses as it ? Runge–Kutta method ?* * Thank you for answering such dull question, but I am so desperate to find any mistake in my code, I have googled but that did not help.
Solution to this problem by Star Strider is to call not the chu2(y) but chu2(~,y)

Best Answer

First, it seems that you are calling your ODE function ‘chu2’ from inside the function, with these lines:
      [~,Y] = ode45(@chu2,[0 1 1]);
      plot3(Y)
Do not do that! Call it from outside your function, in the main script file.
Second, the ODE solvers require 3 arguments, the first one being your ODE function (that you supplied), the second one being vector containing a range [beginning end] or vector of solution times, and the third your initial conditions. It seems you omitted your time vector, the reason you got the error.
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