The revision of our Vanilla Rao-Blackwellisation paper has been accepted by the Annals of Statistics as I was leaving for València 9. This is a very good news, indeed! Especially because I came back from València 9 with an idea on how to extend the Rao-Blackwellisation…
Archive for Valencia 9
Vanilla Rao-Blackwellisation accepted
Posted in Statistics, University life with tags Annals of Statistics, Rao-Blackwellisation, Valencia 9 on June 13, 2010 by xi'anValència 9 papers on line
Posted in Books, Statistics, University life with tags Benidorm, discussions, Valencia 9 on June 11, 2010 by xi'an
Just received this email from José Bernardo:
The pdf files of the Valencia 9 invited papers are now available online at the conference webpage, as a link placed by the author name in the V9 invited program list. These are the last version sent to me by the author, and will be substituted by more current ones as they become available.
I remind you that you are encouraged to submit written contributions to the discussion of any of these 24 papers even if you could not attend the meeting. Your discussions should be directly emailed by June 28th to the author(s) of the invited papers, with a copy to me. I will also need the LaTeX source and the eps files of any figures used. Contributions should not exceed six typeset pages (including figures) for invited discussions, and three pages for contributed discussions.
This means anyone can send discussions on the papers presented at the meeting, to be published soon in the Valencia 9 proceedings by Oxford University Press. We are just out of a post-conference meeting with our students and colleagues here at CREST, where we discussed the invited papers by Ickstadt, Nicholls (actually, sadly not open to written discussions!), Meek, and Wilkinson . (On Monday, we plan to cover Dunson, Früwirth-Schnatter, Lopes, Polson, and Vanucci.)
Impresiónes de València 9
Posted in Mountains, pictures, Statistics, Travel, University life with tags Bayesian non-parametrics, Bayesian statistics, Benidorm, parallelisation, Savage award, sparsity, Valencia 9 on June 10, 2010 by xi'an
The València 9 meeting in Benidorm is now over, even for those who stay till the end of the party (!)… In retrospect, I found the scientific quality of this last meeting of the series quite high and I am thus sad this series comes to an end. This mythical gathering of “true believers” on a Valencianos beach town certainly had a charm not found in other meetings (even though I have no particular love of beaches, of beach towns or of cabarets) in that it brought people really together for a rather long time in an intense and sometime heated exchange of ideas. (This secluded perspective of course reinforced the caricatures of Bayesians as sectarians!) This was particularly true this time as the huge majority of people stayed in the same (awful) hotel. Also, the fact that there was no parallel sessions was a major factor to keep people together… (The fact that the afternoon sessions were administered by ISBA rather than the València 9 scientific committee had the drawback of sometimes producing similar talks.) In my personal view, there were somehow too many non-parametric and sparsity sessions/talks, but this follows the research trends in the community (after all in the 1994 meeting, there were also “too many” MCMC talks!) And the discussions from the floor were much more limited than in the earlier meetings (but most invited discussions were a clear added value to the talks). Maybe this is due to the growing Bayesian community. As in earlier editions, the poster sessions were a strong moment with the frustrating drawback of having too many posters in a single session to allow for a complete coverage (unless you were ready to stay up till 2am…) Again a consequence of the size of the audience. But it was a pleasure to see how Bayesian statistics was well and alive and how the community was bridging old-timers having attending all of the nine Valencia meetings with newcomers still writing their PhD. (Congrats to Emily Fox and to James Scott for their respective Savage awards!)
Darren Wilkinson also gives an overview of the “last Valencia meeting” on his blog. This post includes a detailed analysis of the GPU solution enthusiatically defended by Chris Holmes. Since I came back from the meeting with ideas towards parallel accelerations for MCMC algorithms, I will look carefully at his arguments.
València 9 snapshot [5]
Posted in pictures, Running, Statistics, University life with tags Benidorm, decision theory, intrinsic losses, Lasso, latent variable, reference priors, sparsity, Valencia 9 on June 9, 2010 by xi'an
For the final day of the meeting, after a good one hour run to the end of the Benidorm bay (for me at least!), we got treated to great talks, culminating with the fitting conclusion given by the conference originator, José Bernardo. The first talk of the day was Guido Consonni’s, who introduced a new class of non-local priors to deal with variable selection. From my understanding, those priors avoid a neighbourhood of zero by placing a polynomial prior on the regression coefficients in order to discriminate better between the null and the alternative,
but the influence of the power h seems to be drastic, judging from the example showed by Guido where a move from h=0 to h=1, modified the posterior probability from 0.091 to 0.99 for the same dataset. The discussion by Jim Smith was a perfect finale to the Valencia meetings, Jim being much more abrasive than the usual discussant (while always giving the impression of being near a heart attack//!) The talk from Sylvia Früwirth-Schnatter purposely borrowed Nick Polson’ s title Shrink globally, act locally, and was also dealing with the Bayesian (re)interpretation of Lasso. (I was again left with the impression of hyperparameters that needed to be calibrated but this impression may change after I read the paper!) The talk by Xiao-Li Meng was as efficient as ever with Xiao-Li! Despite the penalising fact of being based on a discussion he wrote for Statistical Science, he managed to convey a global and convincing picture of likelihood inference in latent variable models, while having the audience laugh most of the talk, a feat repeated by his discussant, Ed George. The basic issue of treating latent variables as parameters offers no particular difficulty in Bayesian inference but this is not true for likelihood models, as shown by both Xiao-Li and Ed. The last talk of the València series managed to make a unifying theory out of the major achievements of José Bernardo and, while I have some criticisms about the outcome, this journey back to decision theory, intrinsic losses and reference priors was nonetheless a very appropriate supplementary contribution of José to this wonderful series of meetings…. Luis Perricchi discussed the paper in a very opinionated manner, defending the role of the Bayes factor, and the debate could have gone forever…Hopefully, I will find time to post my comments on José’s paper.
I am quite sorry I had to leave before the Savage prize session where the four finalists to the prize gave a lecture. Those finalists are of the highest quality as the prize is not given in years when the quality of the theses is not deemed high enough. I will also miss the final evening during which the DeGroot Prize is attributed. (When I received the prize for Bayesian Core. in 2004, I had also left in the morning Valparaiso, just before the banquet!)
València 9 snapshot [4]
Posted in Statistics, University life with tags ABC, auxiliary variables, Benidorm, Christchurch, free energy, mixtures, SMC, University of Canterbury, Valencia 9 on June 8, 2010 by xi'an
This one-before-last day at València 9 was fairly busy and I skipped the [tantalising] trip back to Sella to attend morning and afternoon talks. The first session involved Nicolas Chopin and Pierre Jacob’s free-energy paper whose earlier version I had heard at CREST, which builds on the earlier paper of Nicolas with Tony Lelièvre and Gabriel Stoltz to build a sequential Monte Carlo sampler that is biased along a preferential direction in order to fight multimodality and label switching in the case of mixtures. Peter Green rightly pointed out the difficulty in building this direction, which appears like a principal component to me, but this may open a new direction for research on a potentially adaptive direction updated with the SMC sampler… Although I always have trouble understanding the gist of causal models, Thomas Richardson’s talk about transparent parameterisation was quite interesting in its links both with contingency tables and with identifiability issues (should Bayesians care about identifiability?! I did not really understand why the data could help in specifying the unidentified parameter in an empirical Bayes manner, though).
The morning talk by Darren Wilkinson was a particularly enticing talk in that Darren presented in a very articulate manner the specifics of analysing stochastic kinetic models for bacterial regulation and that he also introduced a likelihood-free MCMC that was not ABC-MCMC. (At first sight, it sounds like the auxiliary variable technique of Møller, Pettit, Reeves and Berthelsen, but I want to read the paper to understand better the differences.) Despite the appalling audio and video rendering in the conference room, the filmed discussion by Samuel Kou got into a comparison with ABC. The afternoon non-parametric session left me a bit confused as to the infinite regress on Dirichlet process expansions, but I enjoyed the next talk by Geoff Nicholls on partial ordering inference immensely, even though I missed the bishop example at the beginning because the talks got drifted due to the absence of the first speaker of the session. During the poster session (where again I only saw a fourth of the material!), I had the pleasant surprise to meet a student from the University of Canterbury, Christchurch, who took my Bayesian Core class when I visited in 2006.
