function on a symbolic vector field.

Hello,

x(t) is a symbolic vector field x(t)=[x1(t),x2(t),...,x8(t)] how to define a function handle f=@(x) x(1:3)? This is, if I call y=f(x) it returns a symbolic function y(t)=[x1(t),x2(t),x3(t)] and I can then evaluate y(2)=[x1(2),x2(2),x3(2)] and so on.

What is the right way to do this?