How can I retrieve dY when using ode15i

Hello !

I have a program solving a DAE with ode15i, and the DAE looks like this :

where Y = (x, x1, dx) and therefore dY =(dx, dx1,d²x)

function res = f(t,Y,dY)

l0 = [0.09 0.2];
m_materiel = 265959;

course1 = l0(1) - Y(2);
coursetot = l0(1) + l0(2) - Y(1);
course2 = coursetot - course1;
 
forcemi79 = fmi79(course1,dY(2));
forcemi20 = fmi20(course2,Y(3)-dY(2));


res = [dY(1) - Y(3);
    - forcemi20 + forcemi79;
    dY(3) - 1/m_materiel*(forcemi20)];

Then, for post proccessing, I need to be able to plot dY(2) = dx1, but I don't understand how I can "retrieve" it after using ode15i like this :

[t,y] = ode15i(@f,tspan,y0,yp0)

Can you help ? thank you, have a great day !

Answer 1

[Torsten]

sol = ode15i(@f,tspan,y0,yp0);
[Y,dY] = deval(sol,tspan);
plot(tspan,dY(:,2))

[Zoé Cord'homme]

Thank you so much Torsten !!