Average R-Precision

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The Average R-precision is the arithmetic mean of the R-precision values for an information retrieval system over a set of n query topics. It can be expressed as follows: $$ ARP = {1\over n}\sum\limits_n {RP_n } $$where RP represents the R-Precision value for a given topic from the evaluation set of n topics. R-Precision is defined as the precision after R documents have been retrieved by the system, where R is also the total number of judged relevant documents for the given topic. Precision is defined as the portion of retrieved documents that are truly relevant to the given query topic.

Key Points

R-precision places lower emphasis on the exact ranking of the relevant documents returned by an information retrieval system. This can be useful when a topic has a large number of judged relevant documents, or when an evaluator is more interested in measuring aggregate performance as opposed to the fine-grained quality of the ranking provided by the system.