//MAKESBUS   Builds the vector of complex bus power injections.
//   SBUS = MAKESBUS(BASEMVA, BUS, GEN)
//   SBUS = MAKESBUS(BASEMVA, BUS, GEN, MPOPT, VM)
//   SBUS = MAKESBUS(BASEMVA, BUS, GEN, MPOPT, VM, SG)
//   returns the vector of complex bus power injections, that is, generation
//   minus load. Power is expressed in per unit. If the MPOPT and VM arguments
//   are present it evaluates any ZIP loads based on the provided voltage
//   magnitude vector. If VM is empty, it assumes nominal voltage. If SG is
//   provided, it is a complex ng x 1 vector of generator power injections in
//   p.u., and overrides the PG and QG columns in GEN, using GEN only for
//   connectivity information.
//
//   [SBUS, DSBUS_DVM] = MAKESBUS(BASEMVA, BUS, GEN, MPOPT, VM)
//   With two output arguments, it computes the partial derivative of the
//   bus injections with respect to voltage magnitude, leaving the first
//   return value SBUS empty. If VM is empty, it assumes no voltage dependence
//   and returns a sparse zero matrix.
//
//   See also MAKEYBUS.

//   MATPOWER
//   Copyright (c) 1996-2016, Power Systems Engineering Research Center (PSERC)
//   by Ray Zimmerman, PSERC Cornell
//
//   This file is part of MATPOWER.
//   Covered by the 3-clause BSD License (see LICENSE file for details).
//   See https://matpower.org for more info.

// define named indices into bus, gen matrices

fn make_sbus(baseMVA, bus, gen, mpopt, Vm, Sg) {
    nb = size(bus, 0);
    Sd = make_sdzip(baseMVA, bus, mpopt);
    on = find(slice(gen, [0], [GEN_STATUS-1, GEN_STATUS]) > 0);  // which generators are on?
    gbus = get_multi(slice(gen, [0], [GEN_BUS-1, GEN_BUS]), on) - 1; // what buses are they at?
    ngon = size(on, 0);
    Cg = sparse(gbus, range(0,ngon - 1), 1, nb, ngon);
    return Cg;
}