  We give formulas, in terms of graph theoretical invariants, for the minimum
distance and the generalized Hamming weights of the linear code generated by
the rows of the incidence matrix of a signed graph over a finite field, and for
those of its dual code. Then we determine the regularity of the ideals of
circuits and cocircuits of a signed graph, and prove an algebraic formula in
terms of the multiplicity for the frustration index of an unbalanced signed
graph.
