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Re: [help-GIFT] Effect of Normalization on Recall-Precision

From: Henning Müller
Subject: Re: [help-GIFT] Effect of Normalization on Recall-Precision
Date: Thu, 03 Jul 2003 11:45:16 +0200
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I think that this normalization only makes sure that the similarity value for the pseudo-query image containing all feedback images is 1. This will get the similarity score for most images in between 0 and 1. Without normalization you get higher values but you should still get the exact same order of ranking, thus the same precision and recall values.

This is fairly different when using separate normalization of the four feature groups which does lead to different results as you can see in the following publication, where the two methods are compared with the GIFT system: Henning Müller, David McG. Squire, Wolfgang Müller, Thierry Pun. Efficient access methods for content-based image retrieval with inverted files. In Multimedia Storage and Archiving Systems IV (VV02), Boston, Massachusetts, USA, 20--22~September, 1999 .

Cheers, Henning

Sailesh Suvarna wrote:

Hi all,

  I  have a set of Ranked results taking one ,two and three images as relevant. 
Using the same queries for CIDF with normalization and without normalization ( 
blocking-(*i).second/=fabs(lQueryScore);in and then 
calculating the Recall/Precision and Interpolated Recall Precision, I get the 
same results for both (with and w/o    normalization). I have attached the .ps 
graphs of these results.

  Is the normalization supposed to have any effect on Recall and Precision?

Sailesh Suvarna


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Dr. Henning Müller
University Hospitals of Geneva
Division of Medical Informatics
21, rue Micheli-du-Crest
CH-1211 Geneva 4, Switzerland
Tel  +41 22 372-6175
Fax  +41 22 372-8680
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