/// <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++;
}
}
}
/// <summary>
/// use a queue to pick up all the itemset node and do extension
/// </summary>
private void ItemsetExtension()
{
ItemsetTree = new ItemsetTree <string>();
var root = ItemsetTree.GetRoot;
var queue = new Queue <ItemsetNode <string> >();
var position = 0;
ItemsetNode <string> node;
// first insert all the item in the itemset tree as the children of the root's children
foreach (var item in DataSet.GetItemSILDic())
{
node = ItemsetTree.AddChild(root, new Itemset <string>(item.Key), item.Value, position++);
queue.Enqueue(node);
}
// then pick up every node of the root node'children do the extension
while (queue.Count != 0)
{
node = queue.Dequeue();
ItemsetExtension(ItemsetTree, node);
foreach (var child in node.GetChildren)
{
queue.Enqueue(child);
}
}
}
