The above table covers all meaningful ratios of differentials of I, q, Φm, and V. No device can relate dI to dq, or dΦm to dV, because I is the derivative of q and Φm is the integral of V. It can be inferred from this that memristance is charge-dependent resistance. If M(q(t)) is a constant, then we obtain Ohm's law R(t) = V(t)/I(t). If M(q(t)) is nontrivial, however, the equation is not equivalen