How do i set the initial values in a subs function?

syms c1 c2 k1 k2 m
syms x(t) y(t) s
x_prikk = diff(x(t),t);
x_prikk_prikk = diff(x_prikk,t);
y_prikk = diff(y(t),t);
eq = c2*(y_prikk-x_prikk)-k2*(y-x)-c1*x_prikk-k1*x-m*x_prikk_prikk;

this gives me

eq_s =

k2*(laplace(x(t), t, s) - laplace(y(t), t, s)) - k1*laplace(x(t), t, s) + c2*(x(0) - y(0) - s*laplace(x(t), t, s) + s*laplace(y(t), t, s)) + m*(D(x)(0) + s*x(0) - s^2*laplace(x(t), t, s)) + c1*(x(0) - s*laplace(x(t), t, s))

I'm then aible to set: eq_s_0 = subs(eq_s, {x(0),y(0)},{0,0})

 but how do i set D(x)(0) to "0"?

eq_s_0 = subs(eq_s, {x(0),D(x)(0),y(0)},{0,0,0}) gives me an error: ()-indexing must appear last in an index expression.

[Audrius Indriulionis]

Hi Birger,

You will find an answer on this link<https://se.mathworks.com/matlabcentral/answers/116008-symbolic-math-substitute-a-derivative-function-with-subs Working Walter example at the end of comments>

rgds Audrius