A data frame with 17 columns: hair, feathers, eggs, milk,
  airborne, aquatic, predator, toothed, backbone, breathes, venomous,
  fins, legs, tail, domestic, catsize, type.
Most variables are logical and indicate whether the corresponding
  animal has the corresponsing characteristic or not. The only 2
  exceptions are: legs takes
  values 0, 2, 4, 5, 6, and 8. type is a grouping of the animals
  into 7 groups, see the example section for the detailed list.