The variables are as follows:
id. subjects id
time. Time in weeks after baseline
quit. 0: smoking; 1: quit smoking
sub. patients id
helmert1. Herlmert contrast 1 among 4 treatment groups.
helmert2. Herlmert contrast 2 among 4 treatment groups.
helmert3. Herlmert contrast 3 among 4 treatment groups.
data(skquit)
A data frame with 1861 rows and 6 variables