Is there a way to deal with abstract vectors in the following sense:
Say I have a function f[y]. Now I want to evaluate D[f[x'b], x_j], where x and b are k $\times$ 1 vectors with x_j and b_j as typical elements. Then Mathematica would give me: D[f[x'b], x_j] = f'(.)*b_j.
Can Mathematica deal with vectors in this way?
