Cluster analysis' is a class of statistical techniques that can be applied to data that exhibit "natural" groupings. Cluster analysis sorts through the raw data and groups them into clusters. A cluster is a group of relatively homogeneous cases or observations. Objects in a cluster are similar to each other. They are also dissimilar to objects outside the cluster, particularly objects in other clusters.

E. Backer has written:

'Computer-assisted reasoning in cluster analysis' -- subject(s): Expert systems (Computer science), Cluster analysis, Data processing

H. Charles Romesburg has written:

'Users manual for CLUSTAR/CLUSTID computer programs for hierarchical cluster analysis' -- subject(s): CLUSTAR, CLUSTID, Cluster analysis, Computer programs

The answer depends on the context. One possible answer is cluster analysis.

One answer might be that eh or she is doing cluster analysis. Please see the link.