And k-means clustering — here: http://en.wikipedia.org/wiki/K-means_clustering[^].

Understanding requires some mathematical background, not very complicated, but it should include the understanding of fuzzy set mathematics:

http://en.wikipedia.org/wiki/Fuzzy_set[^],

http://en.wikipedia.org/wiki/Fuzzy_logic[^].

Algorithms are also explained; and even the extensive list of most important implementations, mostly open-source, is provided.

—SA