Solving ODEs using matlab (ode45)

Hello,

I am new to matlab. I was trying to follow an instruction from mit.edu.

I want to use ode45 to solve ODEs.

I have the following in my function page:

function dxy = diffxy (t, xy)
x = xy(1);
xdot = xy(2);
y = xy(3);
xdot = xdot;
ydot = 3*x+5;
xdoubledot = 3-ydot+2*xdot
dxy = [xdot; xdoubledot; ydot]

To get a solution, I type [T, XY] ode45 ('diffxy', 0, 10, [0 1 0]) in my command window (t from 0 to 10 and the initial value of x is 0, xdot is 1, and ydot is 0). But the following message :

??? [T, XY] ode45 ('diffxy', 0 10, [0 1 0])
          |
Error: Unexpected MATLAB expression.

I wonder if anyone could please help.

Thankyou!

Pazzo

[Jan]

What is "my function page"?

I've formatted your code. Please read the "? Help" link to find out, how to do this by your own. Thanks.

You need an additional "=" to assign the output.

Answer 1

[Matt Kindig]

Did you forget the assignment sign?

[T, XY] = ode45 ('diffxy', 0 10, [0 1 0])

[Pazzo Giampalo]

thank you Matt, but no, that didn't work. I guess my question is, when I have the function page written out, how do I call that function (execute it) in my command window? I tried to look up online, but still not figure it out using ode45.

[Jan]

Please explain "didn't work" with details. And we have to know, where you have written the shown code.

Answer 2

[Pazzo]

Jan,

I found out that I should add a bracket, [ ],along with an equal sign, =, to make it work.

thank you for your help though.

Pazzo

Answer 3

[SANDEEP KUMAR R]

Instead of 'diffxy' use @diffxy in ode45