“…The sampling approaches (Aggarwal et al, 2009;Cheng et al, 1998;Guha et al, 1998;Kranen et al, 2011;Lee et al, 2009;Ng et al, 2002;Pal et al, 2002;Sakai et al, 2009;Yildizli et al, 2011) usually choose the samples by a certain rule such as chisquare or divergence hypothesis (Hathaway et al, 2006). The incremental approaches (Bradley et al, 1998;Farnstrom et al, 2000;Gupta et al, 2004;Karkkainen et al, 2007;Luhr et al, 2009;Nguyen-Hoang et al, 2009;Ning et al, 2009;O'Callaghan et al, 2002;Ramakrishnan et al, 1996;Siddiqui et al, 2009;Wan et al, 2010Wan et al, , 2011 generally maintain past knowledge from the previous runs of a clustering algorithm to produce or improve the future clustering model. Nevertheless, as Hore et al (2007) pointed out, many existing algorithms for large and very large data sets are used for the crisp case, rarely for the fuzzy case.…”