Clustering and classification represent the opportunity to apply categorical reasoning to vast data contexts we would otherwise find overwhelming.

Pawel Netzel, Tomasz Stepinski, On Using a Clustering Approach for Global Climate Classification, Journal of Climate, Vol. 29, No. 9 (1 May 2016), pp. 3387-3401 ...

When clustering real data, both c-means and SOM classified observations into clusters that were closer together (relative to k-means) and hence had less distinct boundaries separating the clusters.