NVC_SSL                 Nonparametric Varying Coefficient
                        Spike-and-Slab Lasso (NVC-SSL)
NVC_frequentist         Fits frequentist penalized nonparametric
                        varying coefficient (NVC) models
NVC_predict             Prediction for nonparametric varying
                        coefficient (NVC) models
SimulatedData           Simulated data for illustration
