how to plot solution of differential second order equation ?

i would like to plot "sol3" but i still have this matlab error :

"Error using plot
Conversion to double from sym is not possible."

eq=diff(y,t)/R+C*diff(y,t,2)+y/L==diff(i,t)
Dy = diff(y,t);
cond = [y(0)==0, Dy(0)==0];
sol=dsolve(eq,cond)
sol2=simplify(sol)
sol3=vpa(sol2,2)
T=0:0.001:4;
plot(T, sol3);

[Walter Roberson]

You are trying to solve for two functions, y(t) and i(t), with only one equation, and without any boundary conditions for i(t) . The only way this could work is if i is a pre-defined equation that does not involve partial derivatives of i .

We would have an easier time reproducing your problem if you had given the syms calls and the values for R, C, and L.

Answer 1

[Walter Roberson]

plot(T, subs(sol3, t, T));

[Zina Odfl]

it works ! thank you