We were working on analysing both, papers and code. We wonder if the similarity s(x,y) between two images x and y should be the same as s(y,x). And of course it is. We found that the asymmetry is a normalisation effect, in which the results list is scaled by the score of the query applied on itself. So, when we obtained the scores normalised using the auto-score of the image x, they are slightly different to the scores normalised using the auto-score of the image y.
We just modify the source file CQInvertedFile.cc to avoid this normalization, and now we obtain a symmetric similarity matrix. Thank you very much for your response. Juan C. Caicedo On Thu, Apr 16, 2009 at 4:48 AM, Henning Müller < [email protected]> wrote: > Indeed, the paper: > Tversky, A. (1977). Features of similarity. Psychological Review, 84(4), > 327-352. > shows through epxeriments that our visual similarity percetion does not at > all correspond to a metric. > > Cheers, Henning > > > Wolfgang Müller a écrit : > >> I think the Squire et al. papers from 1999 accessible from the Viper site >> in Geneva cite a paper of Tversky's which justifies asymmetric similarity >> matrices: What you are looking for influences your notion of similarity. >> Cheers, >> Wolfgang >> >> On Thu, Apr 16, 2009 at 8:14 AM, Henning Müller < >> [email protected] <mailto:[email protected]>> >> wrote: >> >> Dear Juan, >> >> this is normal as the similarity measure of GIFT is not a metric as >> it is based on a tf/idf weighting form text retrieval. >> Image similarity is calculated in the space spanned by the features >> present in the query, only. Each image has around 1500 features out >> of 87000 possible (most of them binary features), so each image >> potentially spans a different sub-space in which similarity is >> calculated. >> >> Cheers, Henning >> >> Juan C. Caicedo a écrit : >> >> Hello everybody, >> >> We are building a similarity matrix of an image collection using >> GIFT. However, we notice that this matrix is not a symmetric one. >> Could anybody tells us what is the reason of this behaviour and >> some hints to obtain a symmetric similarity matrix? >> >> Thanks in advance to all you. >> >> Juan C. Caicedo >> >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> help-GIFT mailing list >> [email protected] <mailto:[email protected]> >> http://lists.gnu.org/mailman/listinfo/help-gift >> >> >> >> >> _______________________________________________ >> help-GIFT mailing list >> [email protected] <mailto:[email protected]> >> http://lists.gnu.org/mailman/listinfo/help-gift >> >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> help-GIFT mailing list >> [email protected] >> http://lists.gnu.org/mailman/listinfo/help-gift >> >
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