问题描述
作为生成皮尔逊相关系数，进行如下计算:
As part of the calculations to generate a Pearson Correlation Coefficient, the following computation is performed:
在第二个公式中:p_a,i 是用户a 会给项目i 的预测评分，n 是相似用户的数量ru,i 是用户u 对商品i 的评分.
In the second formula: p_a,i is the predicted rating user a would give item i, n is the number of similar users being compared to, and ru,i is the rating of item i by user u.
如果用户 u 没有评价这个项目，将使用什么值?我在这里误解了什么吗?
What value will be used if user u has not rated this item? Did I misunderstand anything here?
推荐答案
根据链接，算法的第 1 步中的早期计算是在一组项目上进行的，索引为 1 到 m，当m 是共有项的总数.
According to the link, earlier calculations in step 1 of the algorithm are over a set of items, indexed 1 to m, whe m is the total number of items in common.
算法的第 3 步指定:要为特定项目找到特定用户的评分预测，首先选择与当前 用户相关的具有最高加权相似度分数的用户数量对相关项目进行了评分."
Step 3 of the algorithm specifies: "To find a rating prediction for a particular user for a particular item, first select a number of users with the highest, weighted similarity scores with respect to the current user that have rated on the item in question."
这些计算仅在不同用户评分项目集的交集上执行.当用户未对项目评分时，将不会执行任何计算.
These calculations are performed only on the intersection of different users set of rated items. There will be no calculations performed when a user has not rated an item.
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