/// <summary>
/// Method that build a new FPTree starting from i-th header table entry
/// </summary>
/// <param name="i">index of header table entry (head of Conditional Pattern Base)</param>
/// <returns>the created FPTree</returns>
public FPTree CreateFPtree(int i)
{
FPNode ResultRootNode = new FPNode();
FPTree Result = new FPTree();
Result.Root = ResultRootNode;
Result.MinSup = _minSup;
// Counting the frequency of single items
Dictionary <int, int> FrequencyItemCounter2 = new Dictionary <int, int>();
Result.FrequencyItemCounter = FrequencyItemCounter2;
FPNode node;
//Obtain a reference to head of the list of the i.th htrecord
node = ht.GetHead(i);
while (node != default(FPNode))
{
int support;
_travel = node;
support = _travel.Count;
_travel = _travel.Parent;
if (_travel.Parent != default(FPNode))
{
while (_travel.Parent != default(FPNode))
{
if (FrequencyItemCounter2.ContainsKey(_travel.Item))
{
FrequencyItemCounter2[_travel.Item] += support;
}
else
{
FrequencyItemCounter2.Add(_travel.Item, support);
}
_travel = _travel.Parent;
}
}
node = node.Next;
}
//Evaluate header table dimension
int HTsize = 0;
foreach (int item in FrequencyItemCounter2.Keys)
{
if (FrequencyItemCounter2[item] >= _minSup)
{
HTsize++;
}
}
HeaderTable newht = new HeaderTable(HTsize);
Result.ht = newht;
//Insertion of frequent items in header table
foreach (KeyValuePair <int, int> coppia in FrequencyItemCounter2)
{
if (coppia.Value >= _minSup)
{
newht.addRecord(coppia.Key, coppia.Value);
}
}
// Removal of non frequent items, sorting and final insertion in the FPTreee
node = ht.GetHead(i);
while (node != default(FPNode))
{
_travel = node;
ItemSet path = new ItemSet();
path.ItemsSupport = _travel.Count;
_travel = _travel.Parent;
if (_travel.Parent != default(FPNode))
{
while (_travel.Parent != default(FPNode))
{
path.Add(_travel.Item);
_travel = _travel.Parent;
}
ItemSet SortedList = new ItemSet();
SortedList.ItemsSupport = path.ItemsSupport;
foreach (int item in path.Items)
{
if (FrequencyItemCounter2[item] >= _minSup)
{
SortedList.Add(item);
}
}
if (SortedList.Items.Count > 0)
{
SortedList.Items.Sort(new ItemSortingStrategy(FrequencyItemCounter2));
if (Result._depth < SortedList.ItemsNumber)
{
Result._depth = SortedList.ItemsNumber;
}
Result.AddItemSetTree(SortedList, ResultRootNode);
}
}
node = node.Next;
}
return(Result);
}