Longitudinal tapping and UHDRS data for two individuals. There is a steady decline in the number of taps that these two patients are able to perform, with the orange patient (squares) decreasing at a faster rate (A). UHDRS scores gradually increase (worsen) over time, but it is the blue patient (circles) that is deteriorating faster on this measure (B). There is also a good correlation between the two outcomes (C), but this plot loses any reference to time and how these variables represent disease progression. It would be difficult to examine many patients simultaneously on these two measures over time in order to observe trends. These same two individuals are also highlighted (by colour) in Figures 2A, 3A and 3B so that it can be seen how this raw data is represented by vectors.