Python Machine Learning Cookbook

Grouping data using agglomerative clustering

Before we talk about agglomerative clustering, we need to understand hierarchical clustering. Hierarchical clustering refers to a set of clustering algorithms that build tree-like clusters by successively splitting or merging them. This hierarchical structure is represented using a tree.

Hierarchical clustering algorithms can be either bottom-up or top-down. Now what does this mean? In bottom-up algorithms, each datapoint is treated as a separate cluster with a single object. These clusters are then successively merged until all the clusters are merged into a single giant cluster. This is called agglomerative clustering. On the other hand, top-down algorithms start with a giant cluster and successively ...