StagedChoiceSplineMix   Performs iterations between an EM algorithm for
                        a mixture of two-stage logistic regressions
                        with fixed candidate knots and knot movements
bs.se                   Performs a parametric bootstrapping standard
                        error approximation
gen.init                Generates initial values for mixtures of
                        logistic regressions
move.knot               Generates a new set of knots for the following
                        iteration
twostglogitregmixEM     Performs an EM algorithm for mixtures of
                        two-stage logistic regressions
