Cluster analysis can be described as grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to objects in other groups (clusters).
It is generally used for exploratory data analysis and serves as a method of discovery by solving classification issues in many fields, including machine learning, pattern recognition, image analysis, information retrieval, bioinformatics, data compression, and computer graphics.
The result of a cluster analysis shown as the coloring of the squares into three clusters:
