Maybe Pass Extra Parameters to ODE Function at https://www.mathworks.com/help/matlab/ref/ode45.html#bu3uhuk?
Updating the parameter of ODE45
2 views (last 30 days)
Show older comments
I have an ODE system such as
b=1;
f = @(t,x) -(b/N)*x(1)*x(2);
ODE45
I want to write a loop that changes the value of b. But it does not seem to me that just changing the value of b will not update the equation f thus the solution.
b=2;
f = @(t,x) -(b/N)*x(1)*x(2)
ODE45
What should be done here?
2 Comments
Star Strider
on 26 May 2020
That is the best solution. Include both constants in the argument list:
f = @(t,x,b,N) -(b/N)*x(1)*x(2);
then proceed as in the documentation example.
Accepted Answer
Star Strider
on 26 May 2020
Actually, ‘f’ needs to be a (2x1) matrix, since there are two values of ‘x’, and they both need to be defined, so something like this will work:
f = @(t,x,b,N) [x(1); -(b/N)*x(1)*x(2)];
tspan = [0 5];
ic = rand(2,1);
b = rand;
N = 42;
[t,x] = ode45(@(t,x)f(t,x,b,N), tspan, ic);
I am not certain what you are doing, so this may need to be changed. However to integrate two dependent variables, the ODE function has to have that structure, even if you only use the ‘x(:,2)’ result. I would need to know the original differential equation to know if this is correct for it.
4 Comments
Star Strider
on 26 May 2020
That definitely makes sense!
I am still not certain what you are modeling, however that is definitely the correct way to write the ODE function.
More Answers (0)
See Also
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!