Figure 1

A dendrogram of hierarchical clustering of 5 objects. The numbers on the horizon axis represent the indices of objects, and the numbers on the vertical axis represent the distance between any two objects connected. In this example, objects 1 and 3 are merged in the first level; object 4 and 5 are merged in the second level; objects (1, 3) and 2 are merged in the third level; and finally objects (1, 2, 3) and (4, 5) merged in the fourth level. when the dendrogram is cut at the fourth level, two clusters (1, 2, 3) and (4, 5) are obtained; When the dendrogram is cut at the third level, three clusters (1, 2), (3) and (4, 5) are obtained; and so on.