[jira] [Created] (DATAFU-60) Support NDCG calculation within a UDF

["Joshua Hartman (JIRA)" <ji...@apache.org>]

Joshua Hartman created DATAFU-60:
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             Summary: Support NDCG calculation within a UDF
                 Key: DATAFU-60
                 URL: https://issues.apache.org/jira/browse/DATAFU-60
             Project: DataFu
          Issue Type: New Feature
            Reporter: Joshua Hartman


Ndcg is a common evaluation metric for the quality of a list of items presented to a user. It is an especially common metric used in the search literature.

This feature request is to implement a udf to calculate ndcg. 

NDCG can be calculated using any function to represent the value of a position. Several useful functions should be available as part of the datafu library. First is the standard 1/logarithmic discounting factor. Another option should be the ability to supply a custom positional value for any range of positions in the case that a positional "value" is already well understood. However, the actual discounting function used should be easily pluggable in the event something custom is needed



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