Hands-On Data Science with Anaconda

Hierarchical clustering

In hierarchical clustering, the two most similar clusters are combined and continue to combine until all objects are in the same cluster. Hierarchical clustering produces a tree called a dendrogram that shows the hierarchy of the clusters.

To show this concept, let's start by looking at the dataset called animals embedded in the R package called cluster:

> library(cluster) 
> data(animals) 
> dim(animals) 
[1] 20  6 
> head(animals) 
    war fly ver end gro hai 
ant   1   1   1   1   2   1 
bee   1   2   1   1   2   2 
cat   2   1   2   1   1   2 
cpl   1   1   1   1   1   2 
chi   2   1   2   2   2   2 
cow   2   1   2   1   2   2 
> colnames(animals) 
[1] "war" "fly" "ver" "end" "gro" "hai" 
> apply(animals,2, table) # simple overview 
  war fly ver end gro hai 
1  10  16   6  12   6  11 
2  10   4  14   6  11   9 

In total, ...