A data frame containing 613 observations on 5 variables:
RET retinopathy status (1:no retinopathy, 2:nonproliferative retinopathy, 3:advanced retinopathy or
blind)
SM smoker (1:yes, 0:no)
DIAB diabetes duration in years
GH glycosylated hemoglobin measured in percent
BP diastolic blood pressure in mmHg