Python Data Analysis Cookbook

Evaluating clusters with the mean silhouette coefficient

Clustering is an unsupervised machine learning type of analysis. Although we don't know in general what the best clusters are, we can still get an idea of how good the result of clustering is. One way is to calculate the silhouette coefficients as defined in the following equation:

In the preceding equation, a(i) is the average dissimilarity of sample i with respect to other samples in the same cluster. A small a(i) indicates that the sample belongs in its cluster. b(i) is the lowest average dissimilarity of i to other cluster. It indicates the next best cluster for i. If the silhouette coefficients ...