metric.py

#! /usr/bin/python3
# coding=utf-8

'''
    评价
'''
import math


def RMSE(records):
    """计算RMSE
        @param records: 预测评价与真实评价记录的一个list
        @return: RMSE
    """
    numerator = sum([(pred_rating - actual_rating)**2 for pred_rating, actual_rating in records])
    denominator = float(len(records))
    return math.sqrt(numerator / denominator)


def MSE(records):
    """计算MSE
        @param records: 预测评价与真实评价记录的一个list
        @return: MSE
    """
    numerator = sum([(pred_rating - actual_rating)**2 for pred_rating, actual_rating in records])
    denominator = float(len(records))
    return numerator / denominator


def precision(recommends, tests):
    """计算Precision
    :param recommends: dict
        给用户推荐的商品，recommends为一个dict，格式为 { userID : 推荐的物品 }
    :param tests: dict
        测试集，同样为一个dict，格式为 { userID : 实际发生事务的物品 }
    :return: float
        Precision
    """
    n_union = 0.
    user_sum = 0.
    for user_id, items in recommends.items():
        recommend_set = set(items)
        test_set = set(tests[user_id])
        n_union += len(recommend_set & test_set)
        user_sum += len(test_set)

    return n_union / user_sum


def recall(recommends, tests):
    """
        计算Recall
        @param recommends:   给用户推荐的商品，recommends为一个dict，格式为 { userID : 推荐的物品 }
        @param tests:  测试集，同样为一个dict，格式为 { userID : 实际发生事务的物品 }
        @return: Recall
    """
    n_union = 0.
    recommend_sum = 0.
    for user_id, items in recommends.items():
        recommend_set = set(items)
        test_set = set(tests[user_id])
        n_union += len(recommend_set & test_set)
        recommend_sum += len(recommend_set)

    return n_union / recommend_sum


def coverage(recommends, all_items):
    """
        计算覆盖率
        @param recommends : dict形式 { userID : Items }
        @param all_items :  所有的items，为list或set类型
    """
    recommend_items = set()
    for _, items in recommends.items():
        for item in items:
            recommend_items.add(item)
    return len(recommend_items) / len(all_items)


def popularity(item_popular, recommends):
    """计算流行度
        @param item_popular:  商品流行度　dict形式{ itemID : popularity}
        @param recommends :  dict形式 { userID : Items }
        @return: 平均流行度
    """
    popularity = 0.  # 流行度
    n = 0.
    for _, items in recommends.items():
        for item in items:
            popularity += math.log(1. + item_popular.get(item, 0.))
            n += 1
    return popularity / n