A collection of index based algorithms for comparison purposes. Also contains RStarTrees for indexing and the DBSCAN algorithm. Yet, this library is not intended as a library and really is complicated to use (see http://elki.dbs.ifi.lmu.de/wiki/HowTo/InvokingELKIFromJava).
Event-Detection - DBSCAN Algorithm in Map/Reduce logic, implemented with Hadoop and MongoDB, to analyze tweets and photos and to create geolocated events