Editing Cluster analysis (section)

==== [[Silhouette (clustering)|Silhouette coefficient]] ====
The silhouette coefficient contrasts the average distance to elements in the same cluster with the average distance to elements in other clusters. Objects with a high silhouette value are considered well clustered, objects with a low value may be outliers. This index works well with ''k''-means clustering, and is also used to determine the optimal number of clusters.<ref>{{cite journal |title=Silhouettes: A graphical aid to the interpretation and validation of cluster analysis |author=Peter J. Rousseeuw |journal=Journal of Computational and Applied Mathematics |volume=20 |pages=53–65 |year=1987 |doi=10.1016/0377-0427(87)90125-7}}</ref>