how to call odefunction from classdef

I want to call odefunction from classdef, but I don't know the way.

classdef plactice
    properties                       
        L = 1;                       
        m = 1;                    
        g = 9.8;                    
        Tspan = linspace(0,2,20);    
        theta_ic = [0;0];            
        b = 0.01                      
        u = randi([10 25],1,1);
       
    end
    methods
        function [dtheta_dt] = ode_function(t, theta,g,L,u,b)
              
            theta1 = theta(1);
            theta2 = theta(2);
            dtheta1_dt = theta2;
            dtheta2_dt =-(g/L)*(theta1)-b*(theta2)-u;
            dtheta_dt = [dtheta1_dt; dtheta2_dt];
        end
    end
end

The class may be written incorrectly.Is it written correctly?

please someone tell me.

Check the call to the function'ode_function' for incorrect argument data types or missing arguments.

Answer 1

[Steven Lord]

With the way you've written this at least one of the inputs to ode_function must be a plactice object. ode45 won't call your function with either t or y a plactice object.

In addition, I suspect you expect that because the ode_function method has additional input arguments beyond the second required one whose names match the properties of your object that MATLAB will "automatically" pass those property values into your ode_function. That is not the case.

You can do this approach using Constant properties and a Static method. You would call it like:

sol = ode45(@plactice.ode_function, plactice.Tspan, plactice.theta_ic)

Here is the updated definition of plactice.

classdef plactice
    properties(Constant)                       
        L = 1;                       
        m = 1;                    
        g = 9.8;                    
        Tspan = linspace(0,2,20);    
        theta_ic = [0;0];            
        b = 0.01                      
        u = randi([10 25],1,1);
       
    end
    methods(Static)
        function [dtheta_dt] = ode_function(t, theta)
            % Define local variables to make the expression for dtheta2_dt
            % shorter
            g = plactice.g;
            L = plactice.L;
            u = plactice.u;
            b = plactice.b;
              
            theta1 = theta(1);
            theta2 = theta(2);
            dtheta1_dt = theta2;
            dtheta2_dt =-(g/L)*(theta1)-b*(theta2)-u;
            dtheta_dt = [dtheta1_dt; dtheta2_dt];
        end
    end
end

It would be possible to do this with a non-Static method and non-Constant properties, but you would have to pass an instance of your object into ode_function as an additional parameter. The ode45 documentation page includes a link to a page describing a few techniques for passing additional parameters into the ode function.

[ryunosuke tazawa]

Thanks to you, I was able to understand to some extent. However, there is something I would like to know a little more.

What should I do if I define and call the solution derived in ode45 by another function in the class?

classdef plactice
    properties(Constant)             
        L = 1;                  
        m = 1;                      
        g = 9.8;                   
        Tspan = linspace(0,2,20);   
        theta_ic = [0;0];          
        b = 0.01                    
        u = randi([10 25],1,1);
        ball_target = 2.5;
    end
    methods(Static)
        function [dtheta_dt] = ode_function(t, theta)
            
            
            g = plactice.g;
            L = plactice.L;
            u = plactice.u;
            b = plactice.b;
            
            theta1 = theta(1);
            theta2 = theta(2);
            dtheta1_dt = theta2;
            dtheta2_dt =-(g/L)*(theta1)-b*(theta2)-u;
            dtheta_dt = [dtheta1_dt; dtheta2_dt];
        end
         function ball_gosa = ball_function()
                ball_target = plactice.ball_target;
                % ↓error happend here [t. theta]... 
                [t, theta] = ode45(@(t,theta) ode_function(t,theta),plactice.Tspan,plactice.theta_ic);
                w = theta(:,2);                                 
                theta = theta(:,1);    
                ball_x = sin(theta(:,1));
                ball_y = -cos(theta(:,1));
                ball_time = sqrt(2*abs(ball_y)/9.8);   
                ball_reach = ball_x +abs(w)*ball_time;  % No variables assigned
                ball_gosa = ball_rearch-ball_target;

[Steven Lord]

Because ode_function is a Static method, you need to call it using the name of the class.

[t, theta] = ode45(@(t,theta) plactice.ode_function(t,theta),...
    plactice.Tspan,plactice.theta_ic);

[ryunosuke tazawa]

I'm sorry many times. Is the method of defining the function of ball_gosa correct? How can I call it?

[ryunosuke tazawa]

Although theta is recognized. Why are other functions or variables not recognized?

[Steven Lord]

Whenever you call a Static function you need to do so using the name.

q = plactice.ball_gosa()

As long as you fix the typo on the last line of ball_gosa and use element-wise multiplication (.*) instead of matrix multiplication (*) on the next to last line the call will succeed.

[ryunosuke tazawa]

Thank you very much for your help. Thank you for kindly answering the questions to me who just started matlab.