/* Returns C(1), the candidate item sets with size 1 */
public ItemSetTable FindFirstCandidateItemSetTable()
{
ItemSetTable candidateItemSets = new ItemSetTable();
candidateItemSets.order = 1;
SortedSet <int> set = new SortedSet <int>();
foreach (Transaction t in this)
{
foreach (int item in t)
{
set.Add(item);
}
}
foreach (int item in set)
{
ItemSet itemSet = new ItemSet();
itemSet.Add(item);
candidateItemSets.Add(itemSet, 0);
}
IncrementCandidatesIn(candidateItemSets);
return(candidateItemSets);
}
/* Returns L(k+1), candidates in C(k+1) with min_support */
public ItemSetTable BuildFrequentItemSet()
{
int count = 0;
ItemSetTable frequentTable = new ItemSetTable(this.order);
ICollection <ItemSet> keys = new List <ItemSet>(this.Keys);
foreach (ItemSet itemSet in keys)
{
int support = this[itemSet];
if (support >= minSupport)
{
frequentTable.Add(itemSet, support);
++count;
}
}
// If no item set has higher support than min_support, return null.
if (count == 0)
{
return(null);
}
else
{
return(frequentTable);
}
}
/* Returns the candidates C(k+1) generated from L(k) */
public ItemSetTable BuildCandidateItemSet()
{
ItemSetTable candidateTable = new ItemSetTable(this.order + 1);
foreach (ItemSet I1 in this.Keys) // this = L(k)
{
foreach (ItemSet I2 in this.Keys)
{
ItemSet c = null;
IList <int> iList1 = new List <int>(I1);
IList <int> iList2 = new List <int>(I2);
bool joinCondition = false;
for (int i = 0; i < this.order; ++i)
{
// last element
if (i == this.order - 1)
{
if (iList1[i] < iList2[i])
{
joinCondition = true;
}
}
else
{
if (iList1[i] != iList2[i])
{
joinCondition = false;
break;
}
}
}
if (joinCondition == true)
{
c = ItemSet.UnionBetween(I1, I2); // join step: generate candidates
if (hasInfrequentSubSet(c) == false)
{
candidateTable.Add(c, 0);
}
}
}
}
return(candidateTable);
}
