A number of bolts, nails, screws, and tacks are classified according to a number of criteria.
A data frame with the following variables and categories:
Thread: Y = Yes, N = No
Head: F = Flat, C = Cup, O = Cone, R = Round, Y = Cylinder
Head indentation: N = None, T = Star, L = Slit
Bottom: S = Sharp, F = Flat
Length: (in half inches)
Brass: Y = Yes, N = No
Hartigan, J.A. (1975). Clustering Algorithms. New York: Wiley.