Rand index

Description

The Rand index or Rand measure (named after William M. Rand) in statistics, and in particular in data clustering, is a measure of the similarity between two data clusterings. A form of the Rand index may be defined that is adjusted for the chance grouping of elements, this is the adjusted Rand index. From a mathematical standpoint, Rand index is related to the accuracy, but is applicable even when class labels are not used.

Related formulas

Variables

RRand index (dimensionless)
athe number of pairs of elements in S that are in the same subset in X and in the same subset in Y (dimensionless)
bthe number of pairs of elements in S that are in different subsets in X and in different subsets in Y (dimensionless)
nnumber of elements (dimensionless)