pbc3 <- read.csv2("http://staff.pubhealth.ku.dk/~linearpredictors/datafiles/Pbc3.csv",
                  sep = ";",
                  dec = ".",
                  header=TRUE,
                  colClasses =
                  c("factor","factor","factor","factor","numeric",
                    "factor","factor","numeric","numeric",
                    "numeric","numeric","numeric","numeric","numeric","factor"),
                  na.strings="."
                      )

## followup in years
pbc3$followup <- pbc3$days/365.25

## quintiles of bilirubin
## would we like to set the 1st quintile to 0?

quintiles <- quantile(pbc3$bili,seq(0,1,0.2))

## quintile groups of bilirubin
pbc3$biligroup <- cut(pbc3$bili, quintiles,
                      include.lowest=TRUE, # include also lowest observed value
                      labels = c(1:5) # default labelling uses intervals
                      )