Advanced Data Analytics Using Python_ With Machine Learning, Deep Learning and NLP Examples ( 2023)

Chapter 4
Unsupervised Learning: Clustering
end if
end for
end for
K ← K-1;
Cnew ← Cu ∪Cv;
S ← S∪ Cnew –Cu – Cv;
O ← O∪<D, K, S>
Until K = 1;
A Python example of hierarchical clustering is given later in the chapter.
Distance Between Clusters
In hierarchical clustering, calculating the distance between two clusters is
a critical step. There are three methods to calculate this.
• Single linkage method
• Complete linkage method
• Average linkage method
Single Linkage Method
In the single linkage method, the distance between two clusters is the
minimum distance of all distances between pairs of objects in two clusters.
As the distance is the minimum, there will be a single pair of objects that
has less than equal distance between two clusters. So, the single linkage
method may be given as follows:
Dist(C i , C j ) = min dist(X , Y)
X€C i ,Y€C j
90