Change the function in a matrix (diff(f(x), x) to some variable.

Hello,

I want to know if it is possible to change the diff function to a variable which i want to call it like the following. (change it in the answer given by matlab).

• %diff(a(t), t)=a_dot
• %diff(a(t), t, t)=a_doubledot
• %diff(d(t), t)=d_dot
• %diff(d(t), t, t)=d_doubledot
• This is my code:

clc
syms a(t) r d(t) 

r=[d*cos(a);d*sin(a);0];
r_dot=diff(r);
r_doubledot=diff(r_dot);
BCN=[cos(a),sin(a),0;-sin(a),cos(a),0;0,0,1];
br_doubledot=BCN*r_doubledot;
br_doubledot=simplify(br_doubledot)

Answer:
br_doubledot(t) =

                 diff(d(t), t, t) - d(t)*diff(a(t), t)^2
   d(t)*diff(a(t), t, t) + 2*diff(a(t), t)*diff(d(t), t)
                                                       0