Clustering
	• We assume that the data was generated from a number of different classes. The aim is to cluster data from the same class together. – How do we decide the number of classes? • Why not put each datapoint into a separate class? •  What is the payoff for clustering things together? – What if the classes are hierarchical? – What if each datavector can be classified in many different ways? A one-out-of-N classification is not nearly as informative as a feature vector.