Silhouette

Group (Subgroup)

DREAM3D Review (Clustering)

Description

This Filter computes the silhouette for a clustered Attribute Array. The user must select both the original array that has been clustered and the array of cluster Ids. The silhouette represents a measure for the quality of a clustering. Specifically, the silhouette provides a measure for how strongly a given point belongs to its own cluster compared to all other clusters. The silhouette is computed as follows:

\f[ s_{i} = \frac{b_{i} - a_{i}}{\max{a_{i},b_{i}}} \f]

where \f$ a \f$ is the average distance between point \f$ i \f$ and all other points in the cluster point \f$ i \f$ belongs to, \f$ b \f$ is the next closest average distance among all other clusters, and \f$ s \f$ is the silhouette value. Using this definition, \f$ s \f$ exists on the interval \f$ [-1, 1] \f$, where 1 indicates that the point strongly belongs to its current cluster and -1 indicates that the point does not belong well to its current cluster. The user may select from a variety of options to use as the distance metric. Additionally, the user may opt to use a mask array to ignore points in the silhouette; these points will contain a silhouette value of 0.

The silhouette can be used to determine how well a particular clustering has performed, such as k means or k medoids.

Parameters

Name Type Description
Distance Metric Enumeration The metric used to determine the distances between points
Use Mask bool Whether to use a boolean mask array to ignore certain points flagged as false from the algorithm

Required Geometry

None

Required Objects

Kind Default Name Type Component Dimensions Description
Any Attribute Array None Any Any The Attribute Array to silhouette
Attribute Array ClusterIds int32_t (1) Specifies to which cluster each point belongs
Attribute Array Mask bool (1) Specifies if the point is to be counted in the algorithm, if Use Mask is checked

Created Objects

Kind Default Name Type Component Dimensions Description
Attribute Array Silhouette double (1) Silhouette value for each point

Example Pipelines

Please see the description file distributed with this plugin.

DREAM3D Mailing Lists

If you need more help with a filter, please consider asking your question on the DREAM3D Users mailing list: https://groups.google.com/forum/?hl=en#!forum/dream3d-users