calculate_AUC           Function that produces Area Under the
                        Curve(AUC) property for a single individual in
                        a particular group, for a specific metabolite
calculate_Cmax          Function that produces Cmax property for a
                        single individual in a particular group, for a
                        specific metabolite
calculate_Tmax          Function that produces Tmax property for a
                        single individual in a particular group, for a
                        specific metabolite
calculate_half_life     Function that produces Half-life property for a
                        single individual in a particular group, for a
                        specific metabolite
diffGrpResponse         Function that produces a summary table for
                        coefficient estimates, their p-values and LRT
                        p-values for every metabolite in the dataframe
diffGrpResponse_parallel
                        Parallelized version of diffGrpResponse()
gammaFunction           Implementation of the novel non-linear
                        mixed-effects model based on gamma function
                        form with nested covariance structure where
                        random effects are specified for each Diet
                        level within each subject (ID), capturing
                        within-subject correlation across dietary
                        conditions. to identify metabolites that
                        responds to time differentially across dietary
                        groups
generatePlot            Function that generate plots for metabolite
                        models
generate_f_function     Function produce predictions from the model
generate_models         Function that produces a fitted gamma model for
                        each metabolite
grpResp2Time            Function that produces a summary table for
                        coefficient estimates, their p-values and LRT
                        p-values for every metabolite in the dataframe,
                        for a single Group
grpResp2Time_parallel   Vectorized version of grpRes2Time()
pk_calculation          Function that returns a data frame for Tmax,
                        Cmax, half-life, AUC and AUCInf for metabolites
