| insert_bottom | plot-insertion |
| insert_left | plot-insertion |
| insert_right | plot-insertion |
| insert_top | plot-insertion |
| is.ggtree | is.ggtree |
| plot_list | plot a list of ggplot objects |
| xlim2 | xlim2 |
| xrange | plot range of a ggplot object |
| ylim2 | xlim2 |
| yrange | plot range of a ggplot object |