How to Find the Optimal Number of Clusters in Agglomerative Clustering Algorithm?

Data Science, AI and ML
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To find the optimal number of clusters, Silhouette Score is considered to be one of the popular approaches. This technique measures how close each of the observations in a cluster is to the observation in its neighboring clusters.

Let ai be the mean distance between an observation i and other observations in the cluster to which observation i assigned.

Let bi be the minimum mean distance between an observation i and observation in other clusters.

optimal clusters

Conclusion:

  • The range of the Silhouette Scores is from -1 to +1. Higher the value of the Silhouette Score indicates observations are well clustered.
  • Silhouette Score = 1 describes that the data point (i) is correctly and well-matched in the cluster assignment.