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;
}

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 ; }
subtracts an item set from another one .
