generate_2d_n_arms_linked_star_data
                        Generate a 2-dimensional linked star tree data
generate_2d_n_arms_star_data
                        Generate a 2-dimensional star tree data
generate_n_arms_star_data
                        Generate a multi-dimensional star tree data
perturbate_knn          Generate perturbated expression by k-NN data
perturbate_poisson      Generate perturbated counts by the Poisson
                        distribution
plot.treefit            Plot estimated results
treefit                 Estimate the goodness-of-fit between tree
                        models and data
