ODE 45 range for the variables

Hello.

I used ODE45 to solve a system of differential equations dx/dV, dT/dV where V was assigned as t and x,Y as y(1), y(2) respectively. The code works but the numbers are wrong. I want x to be from 0 to 1 and T to be from 298 to 700. How can I implement these inside the ODE function. Is there a way I don't use tspan as a range of the V variable.

Thank you in advance

[Bjorn Gustavsson]

How are you going to get ode45 to understand what range of V you want to integrate your ODEs over if not by the mechanism used for that? And why wouldn't that be OK.

As for the range of x and T you have to define the boundary-conditions. Since these seems to be first-order ODEs you can define the initial conditions of both (or initial condition of one and end-condition of the other and solve this as a boundary-value problem). Then ode45 will integrate over your period-of-interest. If that takes your solution out of the range you expect, then that's a problem of how you've implemented the ODE or your expectations.

HTH

[N/A]

PLEASE HELP (THANK YOU)

Script 2

function dydt=f(t,y)

dydt = [(362*(10.^6).*(1-y(1))*exp(-8731.7./y(2))) ; (8.98.*(10^13).*(1-y(1))*exp(-8731.7./y(2))+17.685.*(10.^3)*(550-y(2)))];

end

Script 1

clear all;

close all;

%x from 0 to 1

%T from 300 to 700

tspan=[0 tmax];

y0=[0 ; 0]; %initial conditions

[t,y] = ode45(@f,tspan,y0);

figure

plot(t,y(:,1));

ylabel('x');

xlabel('V');

title('V-x');

figure

plot(t,y(:,2));

ylabel('T)');

xlabel('V)');

title('V-T');

Answer 1

[Bjorn Gustavsson]

If you want to start your ode-integration at an [x,T]-point of [0,298] you have to define your y0 like this:

y0=[0 ; 298]; %initial conditions

HTH