Abstract: A method and system for performing cluster analysis, particularly in relation to methods of providing purchase recommendations based on analysis of online shopping cart aggregated selections determined using prior collective user activities. One variation of the invention includes the following functions: 1) data is collected at a partner site on a network, such as the Internet; 2) a data stream from the network site is transmitted to a server, and the data is parsed and stored; 3) query logic is used on the database to produce query lists by selected variables; 4) recommendation publishing is invoked by the partner site; 5) recommended data produced using relationships among the collected data is transmitted to the partner site; and 6) the partner site publishes the recommended data.