ABSTRACT
FIGURE 1.1: Smooth longitudinal proles of 16 subjects from the PBC dataset. The solid line represents the t of the loess smoother.
disease progression, and, in particular, we are interested in the association of this marker with survival. The original clinical protocol for these patients specied visits at six months, one year, and annually thereafter. However, due to death and censoring, patients made on average 6.2 visits (st.dev. 3.8 visits), resulting in a total of 1945 observations of serum bilirubin. By the end of the study 140 patients had died, 29 received a transplant, and 143 were still alive. Figure 1.1 shows smoothed longitudinal proles of the log serum bilirubn for a sample of patients, from which it can be seen that many of these proles are nonlinear in time.
