/// <summary>
/// this function used to do item extension , you provide two SIL about item a and b ,it return a SIL about (ab)
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <returns></returns>
public static SparseIdList IStep(SparseIdList a, SparseIdList b)
{
SparseIdList sparseIdList = new SparseIdList(a.GetLength());
ListNode aNode, bNode;
for (int i = 0; i < a.GetLength(); i++)
{
aNode = a.GetElement(i, 0);
bNode = b.GetElement(i, 0);
while ((aNode != null) && (bNode != null))
{
if (aNode.GetSparseId == bNode.GetSparseId)
{
sparseIdList.AddElement(i, aNode.GetSparseId);
aNode = aNode.GetNext;
bNode = bNode.GetNext;
}
else if (aNode.GetSparseId > bNode.GetSparseId)
{
bNode = bNode.GetNext;
}
else
{
aNode = aNode.GetNext;
}
}
}
return(sparseIdList);
}
/// <summary>
/// extension a itemset, we pick up the node's SIL, and its right borther's SIL, we do IStep and if its support bigger than minSupport
/// we neet to merge the itemset of the node whit the item in the last position of the node's right brother's itemset
/// then we insert the new itemset into the itemset tree with the position
/// we store all the itemset in the DataSet's ItemSILDic
/// </summary>
/// <param name="itemsetTree"></param>
/// <param name="node"></param>
private void ItemsetExtension(ItemsetTree <string> itemsetTree, ItemsetNode <string> node)
{
var position = 0;
var children = node.Parent.GetChildren;
for (int i = node.Position + 1; i < children.Count; i++)
{
var rightBrother = children[i];
// var rightBrotherLastItem = rightBrother.Itemset.Last();
// var nodeLastItem = node.Itemset.Last();
// if (!DataSet.CMapIExtension.ContainsKey(nodeLastItem) || !DataSet.CMapIExtension[nodeLastItem].ContainsKey(rightBrotherLastItem))
// {
// continue;
// }
var SIL = SparseIdList.IStep(node.SparseIdList, rightBrother.SparseIdList);
if (SIL.Support >= DataSet.MinSupport)
{
var newItemset = node.Itemset.Clone();
newItemset.AddItems(rightBrother.Itemset.Last());
DataSet.GetItemSILDic().Add(newItemset.Display(), SIL);
itemsetTree.AddChild(node, newItemset, SIL, position);
position++;
}
}
}