Fig. 1

Survival time histogram.The figure shows a typical bimodal distribution of survival time in a longitudinal data set with fitted Weibull distributions at each peak. The fitted Weibull distributions were computed using a maximum likelihood estimation method. The dashed function characterizes the group of short-term survivors, the full line function the long-term survivors. The data used to plot the histogram originates from the “colon” data set, which was originally described in [10] and is provided as part of the R package survival [18]