Adding a vector in a system of differential equations

I have a system of odes to be solved. The problem is that one of the odes contains iapp, which is a vector (same size as the time vector) i have from experimental data.

[time,output]=ode113('DiffEquations',time,init);
with:

function [output] = DiffEquations(time,init)
% defining variables  and constants ...


% output(1,1)=....
% output(2,1)=(....
output(3,1)=(-iNa-iK+iapp)/C;
end

How should i input this vector in the function?

Answer 1

[James Tursa]

One way is to create a function handle to pass in the extra parameters. E.g.,

function [output] = DiffEquations(time,init,iapp) % <-- add iapp to the input argument list

Then in your calling code:

[time,output]=ode113(@(t,y)DiffEquations(t,y,iapp),time,init); % <-- function handle with iapp

[Aria Dae]

Thank you! However, iapp is a vector and i'm getting this error:

Unable to perform assignment because the size of the left side is 1-by-1 and the

size of the right side is 100000-by-1.

Error in DiffEquations (line 118)

output(3,1)=(-iNa-iK+iapp)/C;

How do i add the value of iapp at the index corresponding to the index of the time vector at which this function is being computed?

[James Tursa]

This is telling you that your equation is wrong. If iapp is a vector, how can you possibly assign it to a scalar element of the derivative? You need to re-examine the equations you are simulating and compare it to the code you have written. Or post that for us to see so we can help you.

[Aria Dae]

Sorry for the confusion, i am not explaining myself well. Basilly, i have two vectors of data, the time vector and an Iapp vector (of the same size). What I am trying to compute is the voltage vector ( output(3,1) in the system of odes ) , which can be computed as such : dv/dt=(-iNa-iK+iapp)/C. The first two terms are expressed as functions of time which i wrote above. The iapp term, however, i have as a vector and i don't know how i can add the value of iapp at each second to the corresponding voltage at the same time.

Sorry again for the confusion, and thank you for the help!

[James Tursa]

If you don't know, then that means you don't understand your own set of odes. Is iapp perhaps a time sequence of values that you would need to interpolate? Again, we are guessing here until you can post the odes for us to look at.