Agglomerative Hierarchical Clustering

Implements the Agglomerative Hierarchical Clustering algorithm.

Usage

To run the clustering program, you need to supply the following parameters on the command line:

• Input file that contains the items to be clustered.

• Number of disjointed clusters that we wish to extract.

• Linkage criteria to use when calculating the distance metric.

  • s - Single linkage (default)
  • c - Complete linkage
  • a - Average linkage
  • t - Centroid linkage

For instance, the following is an example run:

$ ./agglomerate example.txt 3 s

In this example, we are running the hierarchical agglomerative clustering on the items in the input file example.txt. We are asking the program to generate 3 disjointed clusters using the single-linkage distance metric.

The input file

The input file contains the items to be clustered.

<number of items to cluster>
<label string>| <x-axis value> <y-axis value>
...

For instance, the following is a valid input. It contains 12 data points, where each data point is referred to by its label and has coordinates in the two-dimensional Euclidean plane.

12
A| 1.0 1.0
B| 2.0 1.0
C| 2.0 2.0
D| 4.0 5.0
E| 5.0 4.0
F| 5.0 5.0
G| 5.0 6.0
H| 6.0 5.0
I| 9.0 9.0
J| 10.0 9.0
K| 10.0 10.0
L| 11.0 9.0

After running the clustering algorithm, we get the following hierarchy:

The cluster hierarchy may be represented by the binary tree:

For further details, please visit my [homepage](http://yaikhom.com/2014/08/21/ agglomerative-hierarchical-clustering.html).