Next: Adjusted Cosine Similarity Up: Item Similarity Computation Previous: Cosine-based Similarity
In this case, similarity between two items i and j is measured by computing the Pearson-r correlation corri,j. To make the correlation computation accurate we must first isolate the co-rated cases (i.e., cases where the users rated both i and j) as shown in Figure 2. Let the set of users who both rated i and j are denoted by U then the correlation similarity is given by
Here Ru,i denotes the rating of user u on item i, is the average rating of the i-th item.
Badrul M. Sarwar