/**
* Creates a new {@link PairSet} instance with the union of all possible transactions and items as
* result for {@link #allTransactions()} and {@link #allItems()}, respectively, and the union of
* pairs.
*
* @param other the other {@link PairSet} instance to merge
* @return the merged {@link PairSet} instance
*/
public PairSet<T, I> merged(PairSet<T, I> other) {
if (other == null) return clone();
// compute the new universe
Set<T> newAllTransactions = new LinkedHashSet<T>(allTransactions);
Set<I> newAllItems = new LinkedHashSet<I>(allItems);
newAllTransactions.addAll(other.allTransactions);
newAllItems.addAll(other.allItems);
// compute the union of pairs
PairSet<T, I> res = new PairSet<T, I>(matrix.clone(), newAllTransactions, newAllItems);
if (!other.isEmpty()) res.addAll(other);
return res;
}
/**
* Creates a new {@link PairSet} instance with only non-empty transactions and items.
*
* @return the compacted {@link PairSet} instance
*/
public PairSet<T, I> compacted() {
// trivial case
if (isEmpty()) return empty();
// compute the new universe
final Set<T> newAllTransactions = new LinkedHashSet<T>(involvedTransactions());
final Set<I> newAllItems = new LinkedHashSet<I>(involvedItems());
if (newAllTransactions.size() == allTransactions.size()
&& newAllItems.size() == allItems.size()) return clone();
// compute the union of pairs
PairSet<T, I> res = new PairSet<T, I>(matrix.empty(), newAllTransactions, newAllItems);
res.addAll(this);
return res;
}