Trouble using the ode45 input

[Stephen23]

You need to parameterize the function call:

https://www.mathworks.com/help/matlab/math/parameterizing-functions.html

See Star Strider's answer for an example of this.

Answer 1

[Sam Chak]

Hi @Isabella

From the ODE, the analytical solution is a sine wave. If the parameters are some fixed values, then you can place them inside the function f.

[t, y] = ode45(@f, [0 15], [-0.9 0]);
plot(t, y), grid on, xlabel('t'), legend('y(t)', 'v(t)')

function dy = f(t, y)
    dy    = zeros(2, 1);
    m     = 4;
    k     = 21;
    omega = sqrt(k/m);
    dy(1) = y(2);
    dy(2) = -(omega^2)*y(1);
end

Answer 2

[Star Strider]

The call to ‘f’ in the ode45 call (and the correct ode45 call) should be:

[t,Y] = ode45(@(t,y)f(t,y,omega0), [0, 15], [y0,v0]);

My MATLAB release (R2023b) can still not run images of code, only actual code. (Perhaps that will be an upgrade in a future release?!)

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