R/is.closed.R

#######################################################################
# arules - Mining Association Rules and Frequent Itemsets
# Copyright (C) 2011-2015 Michael Hahsler, Christian Buchta, 
#			Bettina Gruen and Kurt Hornik
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.



## find closed itemsets
## Nicolas Pasquier, Yves Bastide, Rafik Taouil, and Lotfi Lakhal. (1999) 
## Discovering frequent closed itemsets for association rules. 


setMethod("is.closed", signature(x = "itemsets"),
    function(x) {

        ## An itemset X is closed if no proper super set of X is contained 
        ## in every transaction in which X is contained. Which means there 
        ## exists no super set of X with the same support count as X
        
        ## Check if the set of itemsets is unique in order to
        ## avoid the problem that the same itemset could have
        ## different support counts.
        if (any(is.na(match(x, unique(x), nomatch = NA))))
            stop("itemsets not unique")

        ## R_pnclosed only supports abs. support counts
        cnt <- quality(x)$count
        if(is.null(cnt)) {
            ntrans <-  info(x)$ntransactions
            if(is.null(ntrans)) stop(sQuote("x"), 
                " does not contain sufficient support information (ntransations is missing in info)")
            supp <- quality(x)$support
            if(is.null(supp)) stop(sQuote("x"), 
                " does not contain sufficient support information (support is missing in quality)")
            
            cnt <- as.integer(round(supp * ntrans))
        }
            
        .Call(R_pnclosed, x@items@data, as.integer(cnt), FALSE)
    })

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arules documentation built on Aug. 29, 2019, 9:03 a.m.