question: public final AprioriItemSet subtract ( AprioriItemSet toSubtract ) { AprioriItemSet result = new AprioriItemSet ( m_totalTransactions ) ; result . m_items = new int [ m_items . length ] ; for ( int i = 0 ; i < m_items . length ; i ++ ) { if ( toSubtract . m_items [ i ] == - 1 ) { result . m_items [ i ] = m_items [ i ] ; } else { result . m_items [ i ] = - 1 ; } } result . m_counter = 0 ; return result ; }
target:  Subtracts an item set from another one.