In this article, you will learn. Clustering is the most common form of unsupervised learning on unlabeled data to clusters objects with common characteristics into discrete clusters based on a distance measure. Hierarchical Clustering is either bottom-up, referred to as Agglomerative clustering, or Divisive, which uses a top-down approach. A bottom-up approach where each data point is considered a singleton cluster at the start, clusters are iteratively merged based on similarity until all data points have merged into one cluster. Agglomerative clustering agglomerates pairs of clusters based on maximum similarity calculated using distance metrics to obtain a new cluster, thus reducing the number of clusters with every iteration.

Clustering is the unsupervised learning process of segmenting observations, or dataset into number of groups such that data points have more similarity within the groups than those to the data points in other groups. It is one of the most frequently used analytical process. It helps tremendously in finding of homogeneous groups across the dataset. Clustering algorithms uses different measures to check similarity in order to cluster the observations. The type of similarity measure plays an important role in the final cluster formation.

Clustering is a technique that groups similar objects such that the objects in the same group are more similar to each other than the objects in the other groups. The group of similar objects is called a Cluster. Also called Hierarchical cluster analysis or HCA is an unsupervised clustering algorithm which involves creating clusters that have predominant ordering from top to bottom. For e.g: All files and folders on our hard disk are organized in a hierarchy. The algorithm groups similar objects into groups called clusters.

Exclusive clustering: As the name suggests, exclusive clustering specifies that a data point or object can exist only in one cluster. Hierarchical clustering: Hierarchical tries to create a hierarchy of clusters. There are two types of hierarchical clustering: agglomerative and divisive. Agglomerative follows the bottom-up approach, initially treats each data point as an individual cluster, and the pairs of clusters are merged as they move up the hierarchy. Divisive is the very opposite of agglomerative.

In the early stages of performing data analysis, an important aspect is to get a high level understanding of the multi-dimensional data and find some sort of pattern between the different variables- this is where clustering comes in. This blogpost will focus upon Agglomerative Hierarchical Clustering, its applications and a practical example in R. By now, two questions should arise in your mind. 1) When we say we group the two closest nodes together, how do we define close? And 2) What will be the merging approach to group them? Let's start with a small dataset and understand how Dendrograms are formed in RStudio: I have used normal distribution to compute both x and y coordinates for our dataset and also numbered the datapoints for our understanding. First, we store our x and y datasets as x- and y-coordinates of a dataframe.