how to make a function of this system

how do I make a function of this ?

Answer 1

[Stephan]

syms a b y1(t) y2(t)

ode(1,1) = diff(y1,t,2) == a*y2 - cos(diff(y1,t));
ode(2,1) = diff(y2,t) == b*y1 + cos(t)

ode = 

[V,S] = odeToVectorField(ode)

V = 

S = 

odeFun = matlabFunction(V,'vars',{'t','Y','a','b'})

odeFun = function_handle with value:
    @(t,Y,a,b)[cos(t)+b.*Y(2);Y(3);-cos(Y(3))+a.*Y(1)]

tspan = [0 1];
yInit = [5 0 1];
a = 1;
b = 2;

[t,y] = ode45(@(t,Y)odeFun(t,Y,a,b), tspan, yInit);
plot(t,y)

[Jens Petit-jean]

thanks but is it also possible in a functions script like this?:

function [outputArg1,outputArg2] = untitled5(inputArg1,inputArg2)
%UNTITLED5 Summary of this function goes here
%   Detailed explanation goes here
outputArg1 = inputArg1;
outputArg2 = inputArg2;
end

[Stephan]

Yes, what are the desired in- & outputs?

[Jens Petit-jean]

y(1) and y(2)

[Stephan]

y1 & y2 are the solutions - and due to your system they will only be numerical solutions. They can not be input. So please elaborate what exactly you want to do.

[Jens Petit-jean]

oh yeah sorry I mean dy(1) and dy(2)