Filter可以在评估时根据一定规则来过滤掉部分数据。 Filter的过滤对象是由recommender产生的recommendedList，recommendedList由一组recommendedItem构成，每个recommendedItem表示为一个三元组:(userId itemId value)。
目前支持的过滤器为GenericRecommendedFilter，其功能是返回recommendedList中包含指定userId或itemId的recommendedItem，指定的userId和itemId在GenericRecommendedFilter中以列表的形式提前设置。 目前Filter仅支持在Java代码中使用.
GenericRecommendedFilter过滤效果:
| userIdList = {"1", "2"} |
| recommendedList = { |
| {userId:1 itemId:1 value:1.0}, |
| {userId:1 itemId:2 value:2.0}, |
| {userId:1 itemId:3 value:3.0}, |
| {userId:2 itemId:1 value:4.0}, |
| {userId:2 itemId:2 value:5.0}, |
| {userId:2 itemId:3 value:6.0}, |
| {userId:3 itemId:1 value:7.0}, |
| {userId:3 itemId:2 value:8.0}, |
| {userId:3 itemId:3 value:9.0} |
| } |
| filtered recommendedList = { |
| {userId:1 itemId:2 value:2.0}, |
| {userId:2 itemId:3 value:6.0}, |
| {userId:1 itemId:1 value:1.0}, |
| {userId:2 itemId:1 value:4.0}, |
| {userId:2 itemId:2 value:5.0}, |
| {userId:1 itemId:3 value:3.0} |
| } |
| // specify the userIds and itemIds for filter |
| userIdList = new ArrayList<>(); |
| itemIdList = new ArrayList<>(); |
| for (int i=1; i<=2; i++) { |
| userIdList.add(Integer.toString(i)); |
| itemIdList.add(Integer.toString(4-i)); |
| } |
| // generate recommendedList by recommender |
| Configuration conf = new Configuration(); |
| Resource resource = new Resource("rec/cf/userknn-test.properties"); |
| conf.addResource(resource); |
| DataModel dataModel = new TextDataModel(conf); |
| dataModel.buildDataModel(); |
| RecommenderContext context = new RecommenderContext(conf, dataModel); |
| RecommenderSimilarity similarity = new PCCSimilarity(); |
| similarity.buildSimilarityMatrix(dataModel); |
| context.setSimilarity(similarity); |
| Recommender recommender = new UserKNNRecommender(); |
| recommender.setContext(context); |
| recommender.recommend(context); |
| List<RecommendedItem> recommendedItemList = recommender.getRecommendedList(); |
| // filter the recommendedList with GenericRecommendedFilter |
| GenericRecommendedFilter filter = new GenericRecommendedFilter(); |
| filter.setUserIdList(userIdList); |
| filter.setItemIdList(itemIdList); |
| recommendedItemList = filter.filter(recommendedItemList); |
