www.pudn.com > datamining.rar > L.java

//package cn.edu.tsinghua.ss.liuhongxin; 
 
import java.util.ArrayList; 
 
//import cn.edu.tsinghua.ss.liuhongxin.C; 
//import cn.edu.tsinghua.ss.liuhongxin.Item; 
 
/** 
 * 频繁k-项集 
 */ 
public class L { 
 
  /** 
   * 项的组 
   */ 
  private Item[] items; 
 
  /** 
   * 阶数k 
   */ 
  private int k; 
 
  public L() { 
  } 
 
  public L(Item[] items, int k) { 
    this.items = items; 
    this.k = k; 
  } 
   
  /** 
   * 生成L对应的下一阶c，即由L(k)得到c(k+1) 
   */ 
  public C aprioriGen() { 
    ArrayList cItems = new ArrayList(); 
    for (int i = 0; i < items.length; i++) { 
      // j > i, avoid reduplication. 
      for (int j = i + 1; j < items.length; j++) { 
        if (items[i].similarTo(items[j])) { 
          Item c = items[i].join(items[j]); 
          if (!hasInfrequentSubset(c)) { 
            cItems.add(c); 
          } 
        } 
      } 
    } 
    if (cItems.size() == 0) { 
      return new C(null, k + 1); 
    } else { 
      Item[] theCItems = new Item[cItems.size()]; 
      for (int i = 0; i < cItems.size(); i++) { 
        theCItems[i] = (Item) cItems.get(i); 
      } 
      return new C(theCItems, k + 1); 
    } 
  } 
   
  /** 
   * 判断c中是否存在非频繁子项，在判断是否进行剪裁时使用。 
   */ 
  private boolean hasInfrequentSubset(Item c) { 
    for (int i = 0; i < k; i++) { 
      ArrayList cSubSet = c.getSubSet(i + 1); 
      for (int j = 0; j < cSubSet.size(); j++) { 
        boolean flag = false; 
        for (int l = 0; l < items.length; l++) { 
          if (items[l].getElements().containsAll((ArrayList) cSubSet.get(j))) { 
            flag = true; 
            break; 
          } 
        } 
        if (!flag) { 
          return true; 
        } 
      } 
    } 
    return false; 
  } 
   
  public int getK() { 
    return k; 
  } 
   
  public boolean isEmpty() { 
    if (items == null || items.length == 0) { 
      return true; 
    } else { 
      return false; 
    } 
  } 
 
  public String toString() { 
    StringBuffer returnValue = new StringBuffer("\nFrequent " + k + "-Itemsets:\n"); 
    if (items == null || items.length == 0) { 
      return returnValue.append("EMPTY!").toString(); 
    } 
    for (int i = 0; i < items.length; i++) { 
      returnValue.append(items[i].toString() + ",\n"); 
    } 
    return returnValue.substring(0, returnValue.length() - 2) + "."; 
  } 
 
}