self organizing map and variations implemented in Spark
SOM: https://www.cs.hmc.edu/~kpang/nn/som.html http://lipn.univ-paris13.fr/~cerin/VICHY2014/SARAZIN_TUGDUAL_kptq_TugdualSarazin.pdf #18
SOTA: http://bioinformatics.oxfordjournals.org/content/17/2/126.long
Growing Grid: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.54.8183&rep=rep1&type=pdf
Growing Hierarchy: http://www.ec.tuwien.ac.at/~dieter/research/publications/ijcnn00.pdf
Clutering in general: http://www.hmwu.idv.tw/web/teaching/104-1/EDA/1041-07-hmwu_EDA-Clustering&Vis.pdf