Another commonly used method is hierarchical clustering. In this method, we require to define the distance between data points, the distance between a data point and a cluster, and the distance between clusters. The method generates a dendrogram that is useful to visualize the hierarchy of clusters that are generated, from which a number of clusters can be defined by selecting a threshold or a given maximum distance between data and clusters.

After studying this subsection, you should be able to:

• Implement hierarchical clustering.