如何在Matlab的ode45求解器中更改参数的值 [英] How do I change the value of a parameter inside Matlab's ode45 solver

问题描述

我正在尝试在Matlab中使用ode45求解微分方程.我正在运行两个脚本:

I'm trying to solve a differential equation using ode45 in Matlab. I'm running two scripts:

function xdot=linearproblem(t,x)

global kappa mass F 

xdot(1)=-(kappa/mass)*x(2)+(F/mass)*(cos(omega1*t));
xdot(2)=x(1);

xdot=xdot';

end

然后在第二个脚本中，我有

Then in the second script, I have

close all
clear
clc

global kappa mass F

kappa=4;
F=2;
mass=0.5;
options=odeset('omega1',[1.4 1.5 1.6]);

[t x]=ode45(@linearproblem,0:0.005:100,[0 0],options);
a=x(8000,2);

omega1=omega1'
a=a'

我正在尝试使用omega1的三个值来求解方程，但这给了我一个错误:

I'm trying to solve the equation using three values of omega1, but it's giving me an error:

Error using odeset (line 226)
Unrecognized property name 'omega1'.

Error in frequencysweep (line 12)
options=odeset('omega1',1.4);

我尝试将omega1定义为参数:function xdot=linearproblem(t,x,omega1)，但这无济于事.

I tried defining omega1 as an argument: function xdot=linearproblem(t,x,omega1), but that didn't help.

推荐答案

在

There's no parameter called omega1 in the help or documentation for odeset. That function is for setting the options for ode45 (or the other ODE solvers), not for passing your own values into the integration function.

并且不要使用全局变量. 在这种情况下和大多数其他情况都不需要.而是使用匿名函数来传递参数:

And don't use global variables. There's no need in this case and most others. Instead use an anonymous function to pass the parameters:

@(t,x)linearproblem(t,x,kappa,mass,F)

，并确保linearproblem函数本身也将这些参数用作输入.也许omega1应该以相同的方式传递:

and make sure the linearproblem function itself also takes those parameters as inputs. Maybe omega1 should be passed the same way:

@(t,x)linearproblem(t,x,omega1,kappa,mass,F)

(但是，由于第一个ydot右边的方程式是一个向量，所以会出现错误，但是xdot(1)是单个元素–可能传递omega1(i)并使用for循环呼叫ode45周围?)

(However, you'll get an error as the first ydot equation right-hand-side will be a vector, but xdot(1) is a single element – maybe pass omega1(i) and use a for loop around your calls to ode45?)

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