Assuming that the mathematical form of r(t) is known, the following code snippet will generate a sequence of sampled points from the signal at a sampling rate of Ts:
t = t_start:Ts:(t_end-Ts); %t_start and t_end are the instances of beginning and ending of r(t) respectively.
r_sampled = r(t);
You can go through the following documentation for further help:
