Re: NDCG

["Tetsuya Sakai (office)" <sakai@newswatch.co.jp>]

Thank you everyone, now I understand that Microsoft's nDCG does not have a
"persistence parameter" (the log base).
Sorry about my dumb comments, Nick.

Anyway, which paper was the first to use this version of nDCG?

Dr. Tetsuya Sakai (sakai@newswatch.co.jp)
http://voice.fresheye.com/sakai/

>> From: ireval@nist.gov [mailto:ireval@nist.gov] On Behalf Of Kalervo
>> Jarvelin
>
>> This is a good summary. A point to add is that if one wants to
>> consistently discount the gains, the log(rank+1) variant runs the risk
>> of boosting (instead of discounting) at ranks below the log base. With
>> base=2 this does not matter.
>
> Just a small comment on this.  It is true that the absolute gain values 
> are boosted in those conditions -- however, the relativities still work 
> (the "discounted" gain for rank n+1 is always less than the "discounted" 
> gain for the same relevance value at rank n).  Furthermore, the issue 
> disappears as soon as you normalize.
>
> Stephen