  In this paper we consider Abelian vector plus scalar holographic gravity
models for 2+1 dimensional condensed matter transport, and the effect of
S-duality on them. We find the transport coefficients from the electric and
heat currents via usual membrane paradigm-type calculations, and the effect of
S-duality on them. We study the same system also by using the entropy function
formalism in the extremal case, and the formalism of holographic Stokes
equations, in the case of one-dimensional lattices. We study a few
generalizations that appear when considering a supergravity-inspired model, and
apply the entropy function method for them.
