I would like to create a specific riverplot in R with a numerical x axis. The axis should be from 1 to 100 and the rivers of the "rivers" (which have categories connected to each other) would go until different numbers (in total 4 rivers each with 3 mini-rivers). I made a sketch (but there are only 2 rivers there) of what I want to do. The sketch shows yellow and grey categories too on the right, but actually those should also be on the left somehow. Could anyone help with some suggestions?