Mahout:DataModel doesn't have preference values

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INFO: Processed 943 users

Feb 5, 2011 10:54:31 AM org.slf4j.impl.JCLLoggerAdapter info

INFO: Beginning evaluation using 0.9 of GenericBooleanPrefDataModel[users:1,2,3...]

Exception in thread "main" java.lang.IllegalArgumentException: DataModel doesn't have preference values

at com.google.common.base.Preconditions.checkArgument(Preconditions.java:90)

at org.apache.mahout.cf.taste.impl.similarity.PearsonCorrelationSimilarity.<init>(PearsonCorrelationSimilarity.java:74)

at org.apache.mahout.cf.taste.impl.similarity.PearsonCorrelationSimilarity.<init>(PearsonCorrelationSimilarity.java:66)

at mia.recommender.ch02.RecommenderIntro$6.buildRecommender(RecommenderIntro.java:163)

at org.apache.mahout.cf.taste.impl.eval.AbstractDifferenceRecommenderEvaluator.evaluate(AbstractDifferenceRecommenderEvaluator.java:

124)

at mia.recommender.ch02.RecommenderIntro.eg6(RecommenderIntro.java:175)

at mia.recommender.ch02.RecommenderIntro.main(RecommenderIntro.java:38)　

这个其实,耐心点往后读一点就能看到作者的解释.不过,话说回来,怎样才能将这段代码运行通过呢?究其原因是选择了PearsonCorrelationSimilarity相似度算法,而这个算法是要求偏好值的,所以抛出了" DataModel doesn't have preference values"的异常,我们只需要选适当的相似度算法(或者说不需要偏好值的算法)就可以解决这个问题.这里可选的方案有: Tanimoto coefficient算法和 log-likelihood算法,对应到具体的类:TanimotoCoefficientSimilarity 和 LogLikelihoodSimilarity

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