Predict.matrix.tr.smooth
                        prediction method function for the tr smooth
                        class
add_sim_bound           function dedicated to add simulation standard
                        error bound, in development draw the bound to
                        current plot
air                     dataset from an environmental study.
generate_data           Data generation function for simulation and
                        demonstration A sine-bump setting has been
                        employed.
gplsim                  Function to fit generalized partially linear
                        single-index models via penalized splines
plot_si                 Function that plot fitted curve for the unknown
                        univariate function for single index term
print.summary.gplsim    Print Summary function of gplsim object
si                      An internal function to optimization and
                        fitting.  Don't use it solely.
smooth.construct.tr.smooth.spec
                        supporting function to make tr smooth
summary.gplsim          Summary function of gplsim object
