Key issues Hierarchical clustering is effective when the underlying application requires the creation of a multi-level structure However, they are expensive in terms of their computational and storage requirements In addition once a decision is made to merge two clusters, it cannot be undone at a later time 8/20/2016 PATTERN RECOGNITIONKey issues Hierarchical clustering is effective when the underlying application requires the creation of a multi-level structure. However, they are expensive in terms of their computational and storage requirements. In addition, once a decision is made to merge two clusters, it cannot be undone at a later time. 8/20/2016 PATTERN RECOGNITION 65