Help in solving a system of ODEs using MATLAB

[jcsolis]

Hello, I have been trying to solve this problem and the only thing I got is errors and errors. Also I need to plot y versus t, y' versus t and y' versus y??

Homework Statement

The system of ODEs

y₁'= y₂
y₂'= -2y₁-0.03y₁³

The time span is [0:0.1:5]
and there are no initial conditions!

Need to be solved using ODE45 solver

Homework Equations

None

The Attempt at a Solution

I created this m-file

function yprime = syst1(t, y)
yprime = [y(2); -2*y(1)-0.03*(y(1))^3];

then in the command window

tspan=[0:01:5]
[t y]=oder45 ('syst1', tspan)


and then nothing comes out. I have found many examples of solving systems of ODEs but all of them with initial conditions which is not my case. Can someone explain me waht I am doing wrong?

Than You

 

[mighty2000]

Hello,

Thank you for reaching out for help with your problem. It sounds like you are on the right track, but there are a few things that may be causing errors in your code.

First, in your m-file, you have a typo in the function name. It should be "ode45" instead of "oder45". This could be causing the code to not run properly.

Second, you mentioned that there are no initial conditions given for the system of ODEs. However, the ode45 solver requires initial conditions to solve the system. You will need to specify some initial conditions for y1 and y2 in order for the code to run successfully. These initial conditions can be specified as the third input to the ode45 function, in the form of a vector [y1(0); y2(0)].

Finally, to plot y versus t, y' versus t, and y' versus y, you can use the "plot" function after solving the system. For example, to plot y versus t, you can use the command "plot(t,y(:,1))", where y(:,1) is the first column of the y matrix returned by the ode45 solver.

I hope this helps and good luck with your problem! Let me know if you have any further questions.