Partitional clustering
Partitional clustering decomposes a data set into a set of disjoint clusters. Given a data set of N points, a partitioning method constructs K (N ≥ K) partitions of the data, with each partition representing a cluster.
Partitional clustering decomposes a data set into a set of disjoint clusters. Given a data set of N points, a partitioning method constructs K (N ≥ K) partitions of the data, with each partition representing a cluster. That is, it classifies the data into K groups by satisfying the following requirements: (1) each group contains at least one point, and (2) each point belongs to exactly one group. Notice that for fuzzy partitioning, a point can belong to more than one group.
Many partitional clustering algorithms try to minimize an objective function. For example, in
K-means and
K-medoids the function (also referred to as the distortion function) is
| (1) |
where |
C i | is the number of points in cluster
i, Dist(
x j , center(
i)) is the distance between point
x j and center
i. Many
distance functions can be used, such as Euclidean distance and
L 1 norm.