清空筛选条件
清空筛选条件

ode45 with multiple variables

39 次查看（过去 30 天）
Penglin Cai
Penglin Cai 2020-6-10
评论： madhan ravi 2020-6-10
How can l solve the system with multiple variables using ode45? For example l want to solve the following system for variables x1 x2 y1 y2 with respect to time t:
x1'=x2/4 - (5*x1)/16 + (15*y1)/16 - (3*y2)/4 - x1*(x1^2 + y1^2 - 1) - 3*y1*(x1^2 + y1^2)
y1'= (3*x2)/4 - (15*x1)/16 - (5*y1)/16 + y2/4 + 3*x1*(x1^2 + y1^2) - y1*(x1^2 + y1^2 - 1)
x2'=x1/8 - (5*x2)/16 + x3/8 - (3*y1)/8 + (15*y2)/16 - (3*y3)/8 - x2*(x2^2 + y2^2 - 1) - 3*y2*(x2^2 + y2^2)
y2'=(3*x1)/8 - (15*x2)/16 + (3*x3)/8 + y1/8 - (5*y2)/16 + y3/8 + 3*x2*(x2^2 + y2^2) - y2*(x2^2 + y2^2 - 1)
My question is that is there a simple way to repersent the variables x1 y1 x2 y2 when use ode45 to solve the equations in time rather than defining each variable as A(1)=x1,A(2)=y1A(3)=x2,A(4)=y2
Is there a approach that allows me to:
f=@(t,x1,y1,x2,y2) ...............
[t,R]=(f,tspan,initial condition);
So that i will not need to repersent each variable as the elements in the matrix A. Please help me, thank you very much.

请先登录，再回答此问题。

采纳的回答

madhan ravi
madhan ravi 2020-6-10
Below is the right way to do , but maybe you're looking for matlabFunction()?
Y = zeros(4,1);
Y(1)=x1
Y(2)=y1
Y(3)=x2
Y(4)=y2
  4 个评论
显示 2更早的评论
Bjorn Gustavsson
Bjorn Gustavsson 2020-6-10
If you definitely want to use the variable x1 y1 x2 y2 in your ODE-function (there are often decent enough reasons for this in terms of readability), you simply do something like this up top in your ODE-function:
function dAdt = yourODEfcn(t,A)
x1 = A(1);
x2 = A(2);
y1 = A(3);
y2 = A(4);
% etc
% Then remaining code here
end
madhan ravi
madhan ravi 2020-6-10
Thank you Bjorn was thinking to write in that way but somehow messed it up xD.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Ordinary Differential Equations 的更多信息

标签

产品


版本

R2019b

Community Treasure Hunt

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

Start Hunting!

Translated by