A dendrogram or tree diagram allows to illustrate the hierarchical organisation of several entities. For example, we often use it to make family trees. It is constituted of a root node, which give birth to several nodes that ends by giving leaf nodes (the
bottom of the tree). Dendrogram can be made with 2 types of dataset. i/ a numeric matrixwhere several variables describe the features of individuals. We can then calculate the distance between individuals and clustering them. ii/ A hierarchical
dataset where the relationship between entities is provided directly. These 2 cases are described below. Note that for clusterization, it is a good practice to provide the corresponding heat map that illustrates the structure.