Wünsche nach Mut und Ausdauer nach Wien

1:59:40!

from here to infinity

“Introducing a sparsity prior avoids overfitting the number of clusters not only for finite mixtures, but also (somewhat unexpectedly) for Dirichlet process mixtures which are known to overfit the number of clusters.”

On my way back from Clermont-Ferrand, in an old train that reminded me of my previous ride on that line that took place in… 1975!, I read a fairly interesting paper published in Advances in Data Analysis and Classification by [my Viennese friends] Sylvia Früwirth-Schnatter and Gertrud Malsiner-Walli, where they describe how sparse finite mixtures and Dirichlet process mixtures can achieve similar results when clustering a given dataset. Provided the hyperparameters in both approaches are calibrated accordingly. In both cases these hyperparameters (scale of the Dirichlet process mixture versus scale of the Dirichlet prior on the weights) are endowed with Gamma priors, both depending on the number of components in the finite mixture. Another interesting feature of the paper is to witness how close the related MCMC algorithms are when exploiting the stick-breaking representation of the Dirichlet process mixture. With a resolution of the label switching difficulties via a point process representation and k-mean clustering in the parameter space. [The title of the paper is inspired from Ian Stewart’s book.]

logicomix redux

I had not made the link until the last speaker of the 50 years of Dauphine commemoration was introduced that he was one of the authors of Logicomix. He spoke of the mathematical modeling of neurons and brain activity, rather than comics, but at a very low level that he called cartoonesque. It is a rare event that cartoon characters can be met in the flesh!

Der Kunst ihre Freiheit [and the scare of the nude]

A poster campaign advertising for several exhibits of modernist painters in Vienna, including major paintings by Egon Schiele, has met with astonishing censoring from the transport companies posting these advertisements. (And by Facebook, which AIs are visibly too artificial and none too intelligent to [fail to] recognise well-known works of art.) Not very surprising, given the well-known conservatism of advertising units in transportation companies, but nonetheless appalling, especially when putting these posters against the truly indecent ones advertising for, e.g., gas guzzling machines and junk food.