Apriori算法(C#)

AprioriMethod.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
///AprioriMethod 的摘要说明
/// </summary>
public class AprioriMethod
{

    private readonly static int support = 2; // 支持度阈值
    private readonly static double confidence = 0.7; // 置信度阈值
    private readonly static char[] item_Split = { ';' }; // 项之间的分隔符
    private readonly static string itemSplit = ";";
    private readonly static String CON = "->"; // 项之间的分隔符

    private readonly static List<String> transList = new List<String>(); //所有交易


    public AprioriMethod()
    {
        //
        //TODO: 在此处添加构造函数逻辑
        //
        //初始化交易记录
        transList.Add("移动硬盘;电脑;手机;优盘");
        transList.Add("电脑;优盘;");
        transList.Add("电脑;优盘;");
        transList.Add("手机;电脑;移动硬盘;");
        transList.Add("移动硬盘;手机;");
        transList.Add("电脑;手机;");
        transList.Add("移动硬盘;手机;");
        transList.Add("移动硬盘;电脑;手机;优盘;");
        transList.Add("移动硬盘;电脑;手机;");
       
    }

    public Dictionary<String, int> getFC()   //计算所有频繁项集
    {
        Dictionary<String, int> frequentCollections = new Dictionary<String, int>();//所有的频繁集
        foreach (KeyValuePair<string, int> item in getItem1FC())
        {
            if (frequentCollections.ContainsKey(item.Key))
            {
                frequentCollections.Remove(item.Key);
            }
            frequentCollections.Add(item.Key, item.Value);
        }
        Dictionary<String, int> itemkFcMap = new Dictionary<String, int>();
        foreach (KeyValuePair<string, int> item in getItem1FC())
        {
            itemkFcMap.Add(item.Key, item.Value);
        }

        while (itemkFcMap != null && itemkFcMap.Count != 0)
        {
            Dictionary<String, int> candidateCollection = getCandidateCollection(itemkFcMap);
            List<String> ccKeySet = candidateCollection.Keys.ToList();

            //对候选集项进行累加计数
            foreach (String trans in transList)
            {
                foreach (String candidate in ccKeySet)
                {
                    bool flag = true; // 用来判断交易中是否出现该候选项，如果出现，计数加1
                    String[] candidateItems = candidate.Split(item_Split, StringSplitOptions.RemoveEmptyEntries);
                    foreach (String candidateItem in candidateItems)
                    {
                        if (trans.IndexOf(candidateItem + itemSplit) == -1)
                        {
                            flag = false;
                            break;
                        }
                    }
                    if (flag)
                    {
                        int count = candidateCollection[candidate];
                        candidateCollection.Remove(candidate);
                        candidateCollection.Add(candidate, count + 1);
                    }
                }
            }

            //从候选集中找到符合支持度的频繁集项
            itemkFcMap.Clear();
            foreach (String candidate in ccKeySet)
            {
                int count = candidateCollection[candidate];
                if (count >= support)
                {
                    itemkFcMap.Add(candidate, count);
                }
            }

            //合并所有频繁集
            foreach (KeyValuePair<string, int> item in itemkFcMap)
            {
                if (frequentCollections.ContainsKey(item.Key))
                {
                    frequentCollections.Remove(item.Key);
                }
                frequentCollections.Add(item.Key, item.Value);
            }
        }
        return frequentCollections;
    }



    private Dictionary<String, int> getItem1FC() //计算所有频繁1项集
    {
        Dictionary<String, int> sItem1Fc = new Dictionary<String, int>();
        Dictionary<String, int> rItem1Fc = new Dictionary<String, int>(); //频繁1项集
        foreach (String trans in transList)
        {
            String[] items = trans.Split(item_Split, StringSplitOptions.RemoveEmptyEntries);
            foreach (String item in items)
            {
                int count;
                if (sItem1Fc.ContainsKey(item + itemSplit))
                {
                    count = sItem1Fc[item + itemSplit];
                    sItem1Fc.Remove(item + itemSplit);
                    sItem1Fc.Add(item + itemSplit, count + 1);
                }
                else
                {
                    sItem1Fc.Add(item + itemSplit, 1);
                }
            }
        }
        List<String> keySet = sItem1Fc.Keys.ToList();
        foreach (String key in keySet)
        {
            int count = sItem1Fc[key];
            if (count >= support)
            {
                rItem1Fc.Add(key, count);
            }
        }
        return rItem1Fc;
    }





    private Dictionary<String, int> getCandidateCollection(Dictionary<String, int> itemkFcMap) //生成候选项集
    {
        Dictionary<String, int> candidateCollection = new Dictionary<String, int>();
        List<String> itemkSet1 = itemkFcMap.Keys.ToList();
        List<String> itemkSet2 = itemkFcMap.Keys.ToList();
        foreach (String itemk1 in itemkSet1)
        {
            foreach (String itemk2 in itemkSet2)
            {
                //进行连接
                String[] tmp1 = itemk1.Split(item_Split, StringSplitOptions.RemoveEmptyEntries);
                String[] tmp2 = itemk2.Split(item_Split, StringSplitOptions.RemoveEmptyEntries);

                String c = "";
                if (tmp1.Length == 1)
                {
                    if (tmp1[0].CompareTo(tmp2[0]) < 0)
                    {
                        c = tmp1[0] + itemSplit + tmp2[0] + itemSplit;
                    }
                }
                else
                {
                    bool flag = true;
                    for (int i = 0; i < tmp1.Length - 1; i++)
                    {
                        if (!tmp1[i].Equals(tmp2[i]))
                        {
                            flag = false;
                            break;
                        }
                    }
                    if (flag && (tmp1[tmp1.Length - 1].CompareTo(tmp2[tmp2.Length - 1]) < 0))
                    {
                        c = itemk1 + tmp2[tmp2.Length - 1] + itemSplit;
                    }
                }

                //进行剪枝
                bool hasInfrequentSubSet = false;
                if (!c.Equals(""))
                {
                    String[] tmpC = c.Split(item_Split, StringSplitOptions.RemoveEmptyEntries);
                    for (int i = 0; i < tmpC.Length; i++)
                    {
                        String subC = "";
                        for (int j = 0; j < tmpC.Length; j++)
                        {
                            if (i != j)
                            {
                                subC = subC + tmpC[j] + itemSplit;
                            }
                        }
                        if (!itemkFcMap.ContainsKey(subC))
                        {
                            hasInfrequentSubSet = true;
                            break;
                        }
                    }
                }
                else
                {
                    hasInfrequentSubSet = true;
                }

                if (!hasInfrequentSubSet)
                {
                    candidateCollection.Add(c, 0);
                }
            }
        }
        return candidateCollection;
    }



    public Dictionary<String, Double> getRelationRules(Dictionary<String, int> frequentCollection) //计算关联规则
    {
        Dictionary<String, Double> relationRules = new Dictionary<String, Double>();
        List<String> keySet = frequentCollection.Keys.ToList();
        foreach (String key in keySet)
        {
            double countAll = frequentCollection[key];
            String[] keyItems = key.Split(item_Split, StringSplitOptions.RemoveEmptyEntries);
            if (keyItems.Length > 1)
            {
                List<String> source = keyItems.ToList();

                //Collections.addAll(source, keyItems);
                List<List<String>> result = new List<List<String>>();
                buildSubSet(source, result); //获得source的所有非空子集
                foreach (List<String> itemList in result)
                {
                    if (itemList.Count < source.Count)
                    {   //只处理真子集
                        List<String> otherList = new List<String>();
                        foreach (String sourceItem in source)
                        {
                            if (!itemList.Contains(sourceItem))
                            {
                                otherList.Add(sourceItem);
                            }
                        }
                        String reasonStr = "";//前置
                        String resultStr = "";//结果
                        foreach (String item in itemList)
                        {
                            reasonStr = reasonStr + item + itemSplit;
                        }
                        foreach (String item in otherList)
                        {
                            resultStr = resultStr + item + itemSplit;
                        }
                        double countReason = frequentCollection[reasonStr];
                        double itemConfidence = countAll / countReason;//计算置信度
                        if (itemConfidence >= confidence)
                        {
                            String rule = reasonStr + CON + resultStr;
                            //relationRules.Remove(rule);
                            relationRules.Add(rule, itemConfidence);
                        }
                    }
                }
            }
        }
        return relationRules;
    }



    private void buildSubSet(List<String> sourceSet, List<List<String>> result) //建立频繁项集的子集
    {
        // 仅有一个元素时，递归终止。此时非空子集仅为其自身，所以直接添加到result中
        if (sourceSet.Count == 1)
        {
            List<String> set = new List<String>();
            set.Add(sourceSet[0]);
            result.Add(set);
        }
        else if (sourceSet.Count > 1)
        {
            // 当有n个元素时，递归求出前n-1个子集，在于result中
            buildSubSet(sourceSet.Take(sourceSet.Count - 1).ToList(), result);
            int size = result.Count;// 求出此时result的长度，用于后面的追加第n个元素时计数
            // 把第n个元素加入到集合中
            List<String> single = new List<String>();
            single.Add(sourceSet[sourceSet.Count - 1]);
            result.Add(single);
            // 在保留前面的n-1子集的情况下，把第n个元素分别加到前n个子集中，并把新的集加入到result中;
            // 为保留原有n-1的子集，所以需要先对其进行复制
            List<String> clone;
            for (int i = 0; i < size; i++)
            {
                clone = new List<String>();
                foreach (String str in result[i])
                {
                    clone.Add(str);
                }
                clone.Add(sourceSet[sourceSet.Count - 1]);
                result.Add(clone);
            }
        }
    }


}

Default.aspx.cs

            AprioriMethod apriori = new AprioriMethod();
            Dictionary<String, int> frequentCollection = apriori.getFC();
            Response.Write("----------------频繁集" + "----------------");
            Response.Write("<br/>");
            foreach (var item in frequentCollection)
            {
                Response.Write(item.Key + "-----" + item.Value);
                Response.Write("<br/>");
            }


            Dictionary<String, Double> relationRules = apriori.getRelationRules(frequentCollection);
            Response.Write("----------------关联规则" + "----------------");
            Response.Write("<br/>");
            foreach (var item in relationRules)
            {
                Response.Write(item.Key + "-----" + item.Value);
                Response.Write("<br/>");
            }

结果：

----------------频繁集----------------
移动硬盘;-----6
电脑;-----7
手机;-----7
优盘;-----4
电脑;移动硬盘;-----4
电脑;手机;-----5
电脑;优盘;-----3
手机;移动硬盘;-----6
电脑;手机;移动硬盘;-----4
----------------关联规则----------------
电脑;->手机;-----0.714285714285714
手机;->电脑;-----0.714285714285714
优盘;->电脑;-----0.75
手机;->移动硬盘;-----0.857142857142857
移动硬盘;->手机;-----1
电脑;手机;->移动硬盘;-----0.8
电脑;移动硬盘;->手机;-----1