Choosing an Index¶

Each cluster validity index emphasizes different properties of a partition. Values from different index families are not on a common scale, so compare candidate partitions with the same index rather than comparing one index’s number directly with another’s.

Implemented indices¶
Index	Name	Prefer	Range	Incremental	Remove/merge
`CH`	Calinski–Harabasz	Larger	`[0, inf)`	Yes	Yes
`CONN`	Connectivity	Larger	`[0, 1]`	Fuzzy backend	No
`cSIL`	Centroid-based Silhouette	Larger	`[-1, 1]`	Yes	Yes
`DB`	Davies–Bouldin	Smaller	`[0, inf)`	Yes	Yes
`GD43`	Generalized Dunn 43	Larger	`[0, inf)`	Yes	Yes
`GD53`	Generalized Dunn 53	Larger	`[0, inf)`	Yes	Yes
`PS`	Partition Separation	Larger	`[0, 1]`	Yes	Yes
`rCIP`	Representative Cross Information Potential	Smaller	`[0, inf)`	Yes	Yes
`WB`	Within/Between	Smaller	`[0, inf)`	Yes	Yes
`XB`	Xie–Beni	Smaller	`[0, inf)`	Yes	Yes

CH, DB, GD43, GD53, WB, and XB summarize variants of within-cluster compactness and between-cluster separation. cSIL offers a bounded, centroid-based silhouette measure. PS measures partition separation, while rCIP uses distributional information. CONN is the specialized choice when connectivity between learned prototypes is important; see Using CONN before using it.

The value 0.0 is used when an index is not yet defined, including many one-cluster states. When monitoring a stream, consider the trajectory only after enough clusters and samples have been observed.