HOW TO FIND VELOCITY FROM DISPLACEMENT ?!!

Hi! I'm a student new in MATLAB. I'm trying to find velocity from displacement. I've displacement in a vector of numbers of dimensions double (that means displacement at 75 diferent points, at 83 frame times). Number 2 is because there is longitudinal (1) and radial (2) displacement.

I would like to find longitudinal and radial velocity (I also know that I can do temporal derivative of the displacements because they are small). How should I do it? I have seen there are many functions to derive so I do not know what should I write in my code.

Thanks a lot, guys!