Pendulum equations setup help

%setup : t, starts at 0, with time step dt, until tfinal , which is 1000 seconds.
%initialize the x, ? dot, ? double dot, θ, ? dot, and ? double dots and F vectors as zeros, all the same size as t (time). 
%Set the first value of the θ vector to θ0

t=(0,1000,dt);

%any help on this I really appreciate it