The present invention provides a method of detecting the growth and development of clusters in a data set. The data set is divided into a number of slices and an algorithm is applied to the data held in each data slice set. Each slice can be compared with the subsequent slice to determine which clusters persist from slice to slice. Random data agglomerations in a single slice may give the appearance of a cluster but their random nature means that they are unlikely to persist so those clusters that persist across a number of slices, or that show the strongest measure of persistence, are most likely to represent a data cluster that represents a situation of interest.