[Traminer-users] violation of triangle inequality with future based substitution costs

[Matthias Studer]

Dear Jeremy,

Thank you for pointing this out.

In our first version of the paper, we forgot to take the square root of the result, leading to a squared Euclidean distance that do not garantee the triangle inequality. We corrected this issue in the lastest version of the paper published in the Journal of the Royal Statistical Society: Serie A. However, the change was unfortunately not put in the latest development version of seqdist2. Please excuse us for that. We plan to fix in the next upcoming days.

Future based costs are based on your data, this is why the results depend on your subset.

Best regards,
Matthias


De : traminer-users-bounces at lists.r-forge.r-project.org [mailto:traminer-users-bounces at lists.r-forge.r-project.org] De la part de Jeremy Reynolds
Envoyé : vendredi 14 août 2015 19:57
À : traminer-users at lists.r-forge.r-project.org
Objet : [Traminer-users] violation of triangle inequality with future based substitution costs

Dear Traminer Experts,
I have been using future based substitution costs as described in Studer and Ritschard 2014 and implemented in Traminer to make dissimilarity matrices.  Unfortunately, the results often violate the triangle inequality.  It seems to depend on what subset of my data I use, but I don't really know why the triangle inequality is violated in some cases and not in others.

Is there some appropriate way to fix this (e.g. alter one of the substitution costs manually)?  Does the violation suggest that there is a problem somewhere else in my analysis or suggest something about my data?
I have pasted the output from my latest analysis below in case it is useful.

Thanks,
Jeremy


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