weka实战005：基于HashSet实现的apriori关联规则算法

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这个一个apriori算法的演示版本，所有的代码都在一个类。仅供研究算法参考

package test;import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Vector;//用set写的apriori算法
public class AprioriSetBasedDemo {class Transaction {/** 购物记录，用set保存多个货物名*/private HashSet<String> pnSet = new HashSet<String>();public Transaction() {pnSet.clear();}public Transaction(String[] names) {pnSet.clear();for (String s : names) {pnSet.add(s);}}public HashSet<String> getPnSet() {return pnSet;}public void addPname(String s) {pnSet.add(s);}public boolean containSubSet(HashSet<String> subSet) {return pnSet.containsAll(subSet);}@Overridepublic String toString() {StringBuilder sb = new StringBuilder();Iterator<String> iter = pnSet.iterator();while (iter.hasNext()) {sb.append(iter.next() + ",");}return "Transaction = [" + sb.toString() + "]";}}class TransactionDB {// 记录所有的Transactionprivate Vector<Transaction> vt = new Vector<Transaction>();public TransactionDB() {vt.clear();}public int getSize() {return vt.size();}public void addTransaction(Transaction t) {vt.addElement(t);}public Transaction getTransaction(int idx) {return vt.elementAt(idx);}}public class AssoRule implements Comparable<AssoRule> {private String ruleContent;private double confidence;public void setRuleContent(String ruleContent) {this.ruleContent = ruleContent;}public void setConfidence(double confidence) {this.confidence = confidence;}public AssoRule(String ruleContent, double confidence) {this.ruleContent = ruleContent;this.confidence = confidence;}@Overridepublic int compareTo(AssoRule o) {if (o.confidence > this.confidence) {return 1;} else if (o.confidence == this.confidence) {return 0;} else {return -1;}}@Overridepublic String toString() {return ruleContent + ", confidence=" + confidence * 100 + "%";}}public static String getStringFromSet(HashSet<String> set) {StringBuilder sb = new StringBuilder();Iterator<String> iter = set.iterator();while (iter.hasNext()) {sb.append(iter.next() + ", ");}if (sb.length() > 2) {sb.delete(sb.length() - 2, sb.length() - 1);}return sb.toString();}// 计算具有最小支持度的一项频繁集 >= minSupportpublic static HashMap<String, Integer> buildMinSupportFrequenceSet(TransactionDB tdb, int minSupport) {HashMap<String, Integer> minSupportMap = new HashMap<String, Integer>();for (int i = 0; i < tdb.getSize(); i++) {Transaction t = tdb.getTransaction(i);Iterator<String> it = t.getPnSet().iterator();while (it.hasNext()) {String key = it.next();if (minSupportMap.containsKey(key)) {minSupportMap.put(key, minSupportMap.get(key) + 1);} else {minSupportMap.put(key, new Integer(1));}}}Iterator<String> iter = minSupportMap.keySet().iterator();Vector<String> toBeRemoved = new Vector<String>();while (iter.hasNext()) {String key = iter.next();if (minSupportMap.get(key) < minSupport) {toBeRemoved.add(key);}}for (int i = 0; i < toBeRemoved.size(); i++) {minSupportMap.remove(toBeRemoved.get(i));}return minSupportMap;}public void buildRules(TransactionDB tdb,HashMap<HashSet<String>, Integer> kItemFS, Vector<AssoRule> var,double ruleMinSupportPer) {// 如果kItemFS的成员数量不超过1不需要计算if (kItemFS.size() <= 1) {return;}// k+1项频项集HashMap<HashSet<String>, Integer> kNextItemFS = new HashMap<HashSet<String>, Integer>();// 获得第k项频项集@SuppressWarnings("unchecked")HashSet<String>[] kItemSets = new HashSet[kItemFS.size()];kItemFS.keySet().toArray(kItemSets);/** 根据k项频项集，用两重循环获得k+1项频项集 然后计算有多少个tranction包含这个k+1项频项集* 然后支持比超过ruleMinSupportPer，就可以生成规则，放入规则向量* 然后，将k+1项频项集及其支持度放入kNextItemFS，进入下一轮计算*/for (int i = 0; i < kItemSets.length - 1; i++) {HashSet<String> set_i = kItemSets[i];for (int j = i + 1; j < kItemSets.length; j++) {HashSet<String> set_j = kItemSets[j];// k+1 item setHashSet<String> kNextSet = new HashSet<String>();kNextSet.addAll(set_i);kNextSet.addAll(set_j);if (kNextSet.size() <= set_i.size()|| kNextSet.size() <= set_j.size()) {continue;}// 计算k+1 item set在所有transaction出现了几次int count = 0;for (int k = 0; k < tdb.getSize(); k++) {if (tdb.getTransaction(k).containSubSet(kNextSet)) {count++;}}if (count <= 0) {continue;}Integer n_i = kItemFS.get(set_i);double per = 1.0 * count / n_i.intValue();if (per >= ruleMinSupportPer) {kNextItemFS.put(kNextSet, new Integer(count));HashSet<String> tmp = new HashSet<String>();tmp.addAll(kNextSet);tmp.removeAll(set_i);String s1 = "{" + getStringFromSet(set_i) + "}" + "(" + n_i+ ")" + "==>" + getStringFromSet(tmp).toString()+ "(" + count + ")";var.addElement(new AssoRule(s1, per));}}}// 进入下一轮计算buildRules(tdb, kNextItemFS, var, ruleMinSupportPer);}public void test() {// Transaction数据集TransactionDB tdb = new TransactionDB();// 添加Transaction交易记录tdb.addTransaction(new Transaction(new String[] { "a", "b", "c", "d" }));tdb.addTransaction(new Transaction(new String[] { "a", "b" }));tdb.addTransaction(new Transaction(new String[] { "b", "c" }));tdb.addTransaction(new Transaction(new String[] { "b", "c", "d", "e" }));// 规则最小支持度double minRuleConfidence = 0.5;Vector<AssoRule> vr = computeAssociationRules(tdb, minRuleConfidence);// 输出规则int i = 0;for (AssoRule ar : vr) {System.out.println("rule[" + (i++) + "]: " + ar);}}public Vector<AssoRule> computeAssociationRules(TransactionDB tdb,double ruleMinSupportPer) {// 输出关联规则Vector<AssoRule> var = new Vector<AssoRule>();// 计算最小支持度频项HashMap<String, Integer> minSupportMap = buildMinSupportFrequenceSet(tdb, 2);// 计算一项频项集HashMap<HashSet<String>, Integer> oneItemFS = new HashMap<HashSet<String>, Integer>();for (String key : minSupportMap.keySet()) {HashSet<String> oneItemSet = new HashSet<String>();oneItemSet.add(key);oneItemFS.put(oneItemSet, minSupportMap.get(key));}// 根据一项频项集合，递归计算规则buildRules(tdb, oneItemFS, var, ruleMinSupportPer);// 将规则按照可信度排序Collections.sort(var);return var;}public static void main(String[] args) {AprioriSetBasedDemo asbd = new AprioriSetBasedDemo();asbd.test();}}

运行结果如下：

rule[0]: {d }(2)==>b (2), confidence=100.0%
rule[1]: {d }(2)==>c (2), confidence=100.0%
rule[2]: {d, a }(1)==>c (1), confidence=100.0%
rule[3]: {d, a }(1)==>b (1), confidence=100.0%
rule[4]: {d, a }(1)==>b (1), confidence=100.0%
rule[5]: {d, c }(2)==>b (2), confidence=100.0%
rule[6]: {d, b, a }(1)==>c (1), confidence=100.0%
rule[7]: {d, b, a }(1)==>c (1), confidence=100.0%
rule[8]: {d, c, a }(1)==>b (1), confidence=100.0%
rule[9]: {b }(4)==>c (3), confidence=75.0%
rule[10]: {b, c }(3)==>d (2), confidence=66.66666666666666%
rule[11]: {b, c }(3)==>d (2), confidence=66.66666666666666%
rule[12]: {d }(2)==>a (1), confidence=50.0%
rule[13]: {b }(4)==>a (2), confidence=50.0%
rule[14]: {d, c }(2)==>b, a (1), confidence=50.0%
rule[15]: {d, b }(2)==>a (1), confidence=50.0%

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