clustering algorithms hierarchical clustering introduction to hierarchical clustering hierarchical clustering is another unsupervised learning algorithm that is used to group together the unlabeled data points having similar characteristics hierarchical clustering algorithms falls into following two categoriesagglomerative hierarchical algorithmsin agglomerative hierarchical algorithmseach data point is treated as single cluster and then successively merge or agglomerate (bottom-up approachthe pairs of clusters the hierarchy of the clusters is represented as dendrogram or tree structure divisive hierarchical algorithmson the other handin divisive hierarchical algorithmsall the data points are treated as one big cluster and the process of clustering involves dividing (top-down approachthe one big cluster into various small clusters steps to perform agglomerative hierarchical clustering we are going to explain the most used and important hierarchical clustering agglomerative the steps to perform the same is as followsstep treat each data point as single cluster hencewe will be havingsay clusters at start the number of data points will also be at start step nowin this step we need to form big cluster by joining two closet datapoints this will result in total of - clusters step nowto form more clusters we need to join two closet clusters this will result in total of - clusters step nowto form one big cluster repeat the above three steps until would become no more data points left to join step at lastafter making one single big clusterdendrograms will be used to divide into multiple clusters depending upon the problem role of dendrograms in agglomerative hierarchical clustering as we discussed in the last stepthe role of dendrogram starts once the big cluster is formed dendrogram will be used to split the clusters into multiple cluster of related data points depending upon our problem it can be understood with the help of following exampleexample to understandlet us start with importing the required libraries as follows%matplotlib inline