Testing of Clustering

  • Authors:
  • Noga Alon;Seannie Dar;Michal Parnas;Dana Ron

  • Affiliations:
  • -;-;-;-

  • Venue:
  • SIAM Journal on Discrete Mathematics
  • Year:
  • 2003

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Abstract

A set X of points in $\Re^d$ is (k,b)-clusterable if X can be partitioned into k subsets (clusters) so that the diameter (alternatively, the radius) of each cluster is at most b. We present algorithms that, by sampling from a set X, distinguish between the case that X is (k,b)-clusterable and the case that X is $\epsilon$-far from being (k,b')-clusterable for any given $0k,b')-clusterable we mean that more than $\epsilon\cdot|X|$ points should be removed from X so that it becomes (k,b')-clusterable. We give algorithms for a variety of cost measures that use a sample of size independent of |X| and polynomial in k and $1/\epsilon$.Our algorithms can also be used to find approximately good clusterings. Namely, these are clusterings of all but an $\epsilon$-fraction of the points in X that have optimal (or close to optimal) cost. The benefit of our algorithms is that they construct an implicit representation of such clusterings in time independent of |X|. That is, without actually having to partition all points in X, the implicit representation can be used to answer queries concerning the cluster to which any given point belongs.