MATLAB Answers

how to call odefunction from classdef

4 views (last 30 days)
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.

Accepted Answer

Steven Lord
Steven Lord on 31 Jul 2021
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.
  6 Comments
ryunosuke tazawa
ryunosuke tazawa on 4 Aug 2021
Thank you very much for your help. Thank you for kindly answering the questions to me who just started matlab.

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!