ODE45 solving for three variables

Question

Valeria Moreno 2020-10-23

编辑： Ameer Hamza 2020-10-23

Hello

I am trying to solve for an ODE with

y1'=y2

y2'=y3

y3'=-24y1-26y2-9y3

y(0)=[1 -4 -14]

when I try to code it like this

dydt = [y(2); y(3); -24*y(1)-26*y(2)-9*y(3)];

an error appears

Index exceeds the number of array elements (1).

R_tilde = builtin('subsref',L_tilde,Idx);

I'm pretty new to this so sorry if this is a simple question

Answer 1

Ameer Hamza 2020-10-23

编辑：Ameer Hamza 2020-10-23

You need to write as a function or a function handle

dydt = @(t, y) [y(2); y(3); -24*y(1)-26*y(2)-9*y(3)];
y0 = [1 -4 -14];
tspan = [0 10];
[t, y] = ode45(dydt, tspan, y0);
plot(t, y);