1. What is a Dendrogram?

A Dendrogram demonstrates the hierarchical relationship between objects.

We can think of Dendrograms as a way to represents nested clusters.

2. How to read a Dendrogram?

The key is to focus on the height at which any two objects are joined together.

Look at the image above, we see:

  • E and F are the closest to each other.
  • The cluster of A and B and the cluster of C,D,E and F are the furthest from each other.

3. Applications

An Animal Classes Dendrogram

A Dog Breed Dendrogram

4. Why Dendrogram can be bad?

  • It does not accurately show how many clusters there actually are.

If we cut the single linkage tree at the point shown below, we would say that there are two clusters.

However, if we cut the tree lower we might say that there is one cluster and two singletons.

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