public static ItemsetCollection FindSubsets(Itemset itemset, int n) { ItemsetCollection subsets = new ItemsetCollection(); int subsetCount = (int)Math.Pow(2, itemset.Count); for (int i = 0; i < subsetCount; i++) { if (n == 0 || GetOnCount(i, itemset.Count) == n) { string binary = DecimalToBinary(i, itemset.Count); Itemset subset = new Itemset(); for (int charIndex = 0; charIndex < binary.Length; charIndex++) { if (binary[charIndex] == '1') { subset.Add(itemset[charIndex]); } } subsets.Add(subset); } } return(subsets); }
public static ItemsetCollection DoApriori(ItemsetCollection db, double supportThreshold) { Itemset I = db.GetUniqueItems(); ItemsetCollection L = new ItemsetCollection(); //resultant large itemsets ItemsetCollection Li = new ItemsetCollection(); //large itemset in each iteration ItemsetCollection Ci = new ItemsetCollection(); //pruned itemset in each iteration //first iteration (1-item itemsets) foreach (string item in I) { Ci.Add(new Itemset() { item }); } //next iterations int k = 2; while (Ci.Count != 0) { //set Li from Ci (pruning) Li.Clear(); foreach (Itemset itemset in Ci) { itemset.Support = db.FindSupport(itemset); if (itemset.Support >= supportThreshold) { Li.Add(itemset); L.Add(itemset); } } //set Ci for next iteration (find supersets of Li) Ci.Clear(); Ci.AddRange(Bit.FindSubsets(Li.GetUniqueItems(), k)); //get k-item subsets k += 1; } return(L); }