将额外的依赖于迭代的输入传递给 ode45 [英] Passing additional iteration-dependent inputs to ode45

问题描述

我正在尝试使用 ode45 函数求解微分方程.考虑以下代码，

I'm trying to solve differential equation using the ode45 function. Consider the following code,

[t1,X2] = ode45(@(t,x)fun(t,x,C1,C2,C3,C4),t0,X01);

其中参数 C1、C2、C3 和 C4 是列向量，它们应该可供ode45 所指的函数 (fun.m).我希望每次迭代后都改变值，例如，在开始时，我想要的 C1 条目是 C1(1)，在下一次迭代中它是 C1(2) 等

where parameters C1, C2, C3 and C4 are column vectors, which should be available to the function that ode45 is referring to (fun.m). I want the values to change after every iteration, so for example, at the beginning the entry of C1 I want in is C1(1), in the next iteration it's C1(2), etc.

我该如何实现?

推荐答案

您可能已经注意到 官方文档 在这种情况下并没有太大帮助(因为它们几乎迫使您使用 global 变量 - 这是可行的，但不鼓励).相反，我将向您展示如何使用类和函数句柄来做到这一点.考虑以下几点:

You may have noticed that the official docs are not too helpful in this scenario (as they pretty much force you to use global variables - which is doable, but discouraged). Instead, I'll show you how this can be done with classes and function handles. Consider the following:

classdef SimpleQueue < handle
  %SIMPLEQUEUE A simple FIFO data structure.

  properties (Access = private)
    data
    position
  end

  methods (Access = public)
    function obj = SimpleQueue(inputData)
      %SIMPLEQUEUE Construct an instance of this class
      obj.data = inputData;
      rewind(obj);
    end % constructor

    function out = pop(obj, howMany)
      %POP return the next howMany elements.
      if nargin < 2 
        howMany = 1; % default amount of values to return
      end
      finalPosition = obj.position + howMany;
      if finalPosition > numel(obj.data)
        error('Too many elements requested!');
      end      
      out = obj.data(obj.position + 1 : obj.position + howMany);
      obj.position = finalPosition;      
    end % pop

    function [] = rewind(obj)
      %REWIND restarts the element tracking
      % Subsequent calls to pop() shall return elements from the beginning.
      obj.position = 0;
    end % rewind
  end % methods  
end % classdef

这个怎么用?简单:

C1q = SimpleQueue(C1);
C2q = SimpleQueue(C2);
C3q = SimpleQueue(C3);
C4q = SimpleQueue(C4);

[t1,X2] = ode45(@(t,x)fun(t,x,@C1q.pop,@C2q.pop,@C3q.pop,@C4q.pop),t0,X01);

如您所见，在 fun 中，我们使用 C1q() 而不是 C1.

As you can see, inside fun we use C1q() instead of C1.

这篇关于将额外的依赖于迭代的输入传递给 ode45的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！