Agglomerative Clustering is a type of hierarchical clustering that takes the bottom-up approach
Algorithm
agglomerative-clustering(points) {
each point is its own cluster
repeat until one cluster left:
pick 2 "CLOSEST" clusters
merge them into new cluster
return that cluster
}
produces a family of clusterings represented by a dendrogram
Defining “Closest” for Clusters of Multiple Elements
- closest pair (single-link clustering)
- farthest pair (complete-link clustering)
- average of all pairs
- Ward’s Method (min variance, likek-means) - find pair of clusters that leads to minimum increase in total within cluster distance after merging