package pearsonCorrelationScore;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
/**
 * @author shenchao
 *
 *     皮尔逊相关度评价
 *
 *     以《集体智慧编程》一书用户评价相似度数据集做测试
 */
public class PearsonCorrelationScore {
 private Map<String, Map<String, double>> dataset = null;
 public PearsonCorrelationScore() {
  initDataSet();
 }
 /**
* 初始化数据集
*/
 private void initDataSet() {
  dataset = new HashMap<String, Map<String, double>>();
  // 初始化Lisa Rose 数据集
  Map<String, double> roseMap = new HashMap<String, double>();
  roseMap.put("Lady in the water", 2.5);
  roseMap.put("Snakes on a Plane", 3.5);
  roseMap.put("Just My Luck", 3.0);
  roseMap.put("Superman Returns", 3.5);
  roseMap.put("You, Me and Dupree", 2.5);
  roseMap.put("The Night Listener", 3.0);
  dataset.put("Lisa Rose", roseMap);
  // 初始化Jack Matthews 数据集
  Map<String, double> jackMap = new HashMap<String, double>();
  jackMap.put("Lady in the water", 3.0);
  jackMap.put("Snakes on a Plane", 4.0);
  jackMap.put("Superman Returns", 5.0);
  jackMap.put("You, Me and Dupree", 3.5);
  jackMap.put("The Night Listener", 3.0);
  dataset.put("Jack Matthews", jackMap);
  // 初始化Jack Matthews 数据集
  Map<String, double> geneMap = new HashMap<String, double>();
  geneMap.put("Lady in the water", 3.0);
  geneMap.put("Snakes on a Plane", 3.5);
  geneMap.put("Just My Luck", 1.5);
  geneMap.put("Superman Returns", 5.0);
  geneMap.put("You, Me and Dupree", 3.5);
  geneMap.put("The Night Listener", 3.0);
  dataset.put("Gene Seymour", geneMap);
 }
 public Map<String, Map<String, double>> getDataSet() {
  return dataset;
 }
 /**
* @param person1
*      name
* @param person2
*      name
* @return 皮尔逊相关度值
*/
 public double sim_pearson(String person1, String person2) {
  // 找出双方都评论过的电影,（皮尔逊算法要求）
  List<String> list = new ArrayList<String>();
  for (Entry<String, double> p1 : dataset.get(person1).entrySet()) {
   if (dataset.get(person2).containsKey(p1.getKey())) {
    list.add(p1.getKey());
   }
  }
  double sumX = 0.0;
  double sumY = 0.0;
  double sumX_Sq = 0.0;
  double sumY_Sq = 0.0;
  double sumXY = 0.0;
  int N = list.size();
  for (String name : list) {
   Map<String, double> p1Map = dataset.get(person1);
   Map<String, double> p2Map = dataset.get(person2);
   sumX += p1Map.get(name);
   sumY += p2Map.get(name);
   sumX_Sq += Math.pow(p1Map.get(name), 2);
   sumY_Sq += Math.pow(p2Map.get(name), 2);
   sumXY += p1Map.get(name) * p2Map.get(name);
  }
  double numerator = sumXY - sumX * sumY / N;
  double denominator = Math.sqrt((sumX_Sq - sumX * sumX / N)
  * (sumY_Sq - sumY * sumY / N));
  // 分母不能为0
  if (denominator == 0) {
   return 0;
  }
  return numerator / denominator;
 }
 public static void main(String[] args) {
  PearsonCorrelationScore pearsonCorrelationScore = new PearsonCorrelationScore();
  System.out.println(pearsonCorrelationScore.sim_pearson("Lisa Rose",
  "Jack Matthews"));
 }
}