Clustering
Being able to find groups of similar data that exist in your dataset can be extremely valuable if you are trying to find its underlying meaning. If you were a store owner and you wanted to understand which customers are more valuable without a set idea of what valuable is, clustering would be a great place to start to find patterns in your data. You may have a few high-level ideas of what denotes a valuable customer, but you aren't entirely sure in the face of a large mountain of available data. Through clustering you can find commonalities among similar groups in your data. If you look more deeply at a cluster of similar people, you may learn that everyone in that group visits your website for longer periods of time than others. This can show you what the value is and also provides a clean sample size for future supervised learning experiments.
Identifying Clusters
The following figure shows two scatterplots:
