How do I get ode45 to output the dependent variable value at each time step? I have other material properties in my differential equation that change with temperature, so I must update them with each change in temperature.

the equation looks like this:

dT/dt = T/cB(T,B) * d/dT( M(T)) * d/dt( B(t))

cB(T) = the specific heat M(T) = the magnetization of the material

Answer 1

[Jonathan Epperl]

The answer to your topic is that the odefun, i.e. the function you pass to ode45 as in ode45(odefun,tspan,x0) needs include the line

y

as in

function dydt = odefun(t,y)
%[...] code
y

but I don't think that's what you really want to do/know. Could you detail your question? Also, what is B(t), is that another state you're not telling us about, or is that a known function/input?

Is there a closed form of M(T), cB(T,B) that you are using, or is it a look-up table?

[David Campbell]

Thank you for getting back to me so quickly Jonathan.

I've been looking into it, and yes I think you're right, I'm going to have to include a section in the odefun for this.

To answer your question B(t) is a magnetic wave form:

B(t) = -0.5cos((2*pi/5)t) + 0.5 (ie a wave that will go through one full cycle over the time span I will set for this ode45)

I'm not sure what closed form means exactly but M(T,B) and cB(T,B) are both matrices that give the value of M and cB at different T and B. They are calculated by another program I have written, but the matrices I have calculated will definitely cover the temperature and magnetic field ranges that will occur within this differential equation.

Cheers, Oliver