ode45 with multiple variables
24 views (last 30 days)
Show older comments
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.
0 Comments
Accepted Answer
madhan ravi
on 10 Jun 2020
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 Comments
Bjorn Gustavsson
on 10 Jun 2020
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
on 10 Jun 2020
Thank you Bjorn was thinking to write in that way but somehow messed it up xD.
More Answers (0)
See Also
Categories
Find more on Ordinary Differential Equations in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!