geom_bump               geom_bump Creates a ggplot that makes a smooth
                        rank over time. To change the 'smooth' argument
                        you need to put it outside of the 'aes' of the
                        geom. Uses the x and y aestethics.
geom_sigmoid            geom_sigmoid Creates a ggplot that makes a
                        smooth rank over time. To change the 'smooth'
                        argument you need to put it outside of the
                        'aes' of the geom. Uses the x, xend, y and yend
                        aestethics. Make sure each sigmoid curve is its
                        own group.
rank_sigmoid            rank_sigmoid Creates a longer dataframe with
                        coordinates for a smoothed line.
sigmoid                 sigmoid Creates a longer dataframe with
                        coordinates for a smoothed line.
