MATLAB: Pass class function handle to ode45()?

Question

I have a class function that uses ODE45 to solve some equations. I have another, private class function that represents the odefunction that ODE45 needs to solve. However, I can't figure out how to pass a handle of the class's ode function to ODE45. Here is the sample code:

class ODESolver < handle

    methods (Access = public)

        function obj = RunODE(obj, t, y0)
            [~, Z] = ode45(@ODEFunction, t, y0);
        end

    end

    methods (Access = private)

        function dy = ODEFunction(t,y)
            % Calculate dy here.
        end

    end

end

When I run this, i get an error saying:

Undefined function 'ODEFunction' for input arguments of type 'double'.

If I move ODEFunction outside of the class and put it in its own *.m file, the code runs fine. I've also tried using "@obj.ODEFunction" in the ode45 call, but then it says:

Too many input arguments.

What's the best way to keep ODEFunction inside of my class and still be able to pass it's handle to ode45?

CitizenInsane · Accepted Answer · 2015-02-13T17:59:37.057

2

Your private ODEFunction is not a static method, so you should write:

classdef ODESolver < handle

    methods (Access = public)

        function obj = RunODE(obj, t, y0)
            [~, Z] = ode45(@(tt, yy)obj.ODEFunction(tt, yy), t, y0);
        end

    end

    methods (Access = private)

        function dy = ODEFunction(obj, t,y)
            dy = 0.1; % Calculate dy here.
        end

    end

end

NB: You also forgot to pass obj as first argument of private ODEFunction ... I'm writing example with static method and will paste it here once tested.

Edit

Here is how you should write things if you intented to have private static ODEFunction in your class:

classdef ODESolver < handle

    methods (Access = public)

        function obj = RunODE(obj, t, y0)
            [~, Z] = ode45(@(tt, yy)ODESolver.ODEFunction(tt, yy), t, y0);
        end

    end

    methods (Static, Access = private)

        function dy = ODEFunction(t,y)
            dy = 0.1; % Calculate dy here.
        end

    end

end

edited Feb 13 '15 at 17:59

answered Feb 13 '15 at 17:53

CitizenInsane

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Awesome, will try this out after lunch. What is the significance of (tt, yy)? – pcdangio Feb 13 '15 at 18:04
This is syntaxic sugar to ease readiness. Personnally, when I write an anonymous method I prefer to write `@(*parameters as passed by the caller*)MyFunction(*parameters that i want to effectively pass to MyFunction*)` .... this also works with `varargin` and local scope variables: `@(varargin)MyFunction(localScopeVariable, varargin{end:-1:1})` – CitizenInsane Feb 13 '15 at 18:12
Here is also more details for why to use `@MyClass.MyMethod` with static methods and `@obj.MyMethod` (or `@(varargin)MyMethod(obj, varargin{:})` ) with non static ones : http://fr.mathworks.com/help/matlab/matlab_oop/class-methods-for-graphics-callbacks.html – CitizenInsane Feb 13 '15 at 18:22
1

Thanks for all the info. Just tried it out, works like a charm! – pcdangio Feb 13 '15 at 18:34
U're welcome ... You'll see, writing anonymous function becomes easier with time ... ;) – CitizenInsane Feb 13 '15 at 19:44

MATLAB: Pass class function handle to ode45()?

1 Answers1