## Cancun, ISBA 2014 [½ day #2]

Posted in pictures, Running, Statistics, Travel, University life with tags , , , , , , , , , , , , on July 19, 2014 by xi'an

Half-day #2 indeed at ISBA 2014, as the Wednesday afternoon kept to the Valencia tradition of free time, and potential cultural excursions, so there were only talks in the morning. And still the core poster session at (late) night. In which my student Kaniav Kamari presented a poster on a current project we are running with Kerrie Mengersen and Judith Rousseau on the replacement of the standard Bayesian testing setting with a mixture representation. Being half-asleep by the time the session started, I did not stay long enough to collect data on the reactions to this proposal, but the paper should be arXived pretty soon. And Kate Lee gave a poster on our importance sampler for evidence approximation in mixtures (soon to be revised!). There was also an interesting poster about reparameterisation towards higher efficiency of MCMC algorithms, intersecting with my long-going interest in the matter, although I cannot find a mention of it in the abstracts. And I had a nice talk with Eduardo Gutierrez-Pena about infering on credible intervals through loss functions. There were also a couple of appealing posters on g-priors. Except I was sleepwalking by the time I spotted them… (My conference sleeping pattern does not work that well for ISBA meetings! Thankfully, both next editions will be in Europe.)

Great talk by Steve McEachern that linked to our ABC work on Bayesian model choice with insufficient statistics, arguing towards robustification of Bayesian inference by only using summary statistics. Despite this being “against the hubris of Bayes”… Obviously, the talk just gave a flavour of Steve’s perspective on that topic and I hope I can read more to see how we agree (or not!) on this notion of using insufficient summaries to conduct inference rather than trying to model “the whole world”, given the mistrust we must preserve about models and likelihoods. And another great talk by Ioanna Manolopoulou on another of my pet topics, capture-recapture, although she phrased it as a partly identified model (as in Kline’s talk yesterday). This related with capture-recapture in that when estimating a capture-recapture model with covariates, sampling and inference are biased as well. I appreciated particularly the use of BART to analyse the bias in the modelling. And the talk provided a nice counterpoint to the rather pessimistic approach of Kline’s.

Terrific plenary sessions as well, from Wilke’s spatio-temporal models (in the spirit of his superb book with Noel Cressie) to Igor Prunster’s great entry on Gibbs process priors. With the highly significant conclusion that those processes are best suited for (in the sense that they are only consistent for) discrete support distributions. Alternatives are to be used for continuous support distributions, the special case of a Dirichlet prior constituting a sort of unique counter-example. Quite an inspiring talk (even though I had a few micro-naps throughout it!).

I shared my afternoon free time between discussing the next O’Bayes meeting (2015 is getting very close!) with friends from the Objective Bayes section, getting a quick look at the Museo Maya de Cancún (terrific building!), and getting some work done (thanks to the lack of wireless…)

## MCMSki IV, Jan. 6-8, 2014, Chamonix (news #18)

Posted in Mountains, R, Statistics, University life with tags , , , , , , , , , , , , on January 6, 2014 by xi'an

MCMSki IV is about to start! While further participants may still register (registration is still open!), we are currently 223 registered participants, without accompanying people. I do hope most of these managed to reach the town of Chamonix-Mont-Blanc despite the foul weather on the East Coast. Unfortunately, three speakers (so far) cannot make it: Yugo Chen (Urbana-Champaign), David Hunter (Penn State), Georgios Karagiannis (Toronto), and Liam Paninski (New York). Nial Friel will replace David Hunter and give a talk on Noisy MCMC.

First, the  posters for tonight session (A to K authors) should be posted today (before dinner) on the boards at the end of the main lecture theatre. And removed tonight as well. Check my wordpress blog for the abstracts. (When I mentioned there was no deadline for sending abstracts, I did not expect getting one last Friday!)

Second, I remind potential skiers that the most manageable option is to ski on the Brévent domain, uphill from the conference centre. There is even a small rental place facing the cable-car station (make sure to phone +33450535264 to check they still have skis available) and renting storage closets…

## MCMSki IV, Jan. 6-8, 2014, Chamonix (news #17)

Posted in Mountains, R, Statistics, University life with tags , , , , , , , , , , , , , on January 3, 2014 by xi'an

We are a few days from the start, here are the latest items of information for the participants:

The shuttle transfer on January 5th, from Geneva Airport to Chamonix lasts 1 hour 30 minutes. At your arrival in the airport , follow the “Swiss Exit”. After the customs, the bus driver (handling a sign “MCMC’Ski Chamonix”) will be waiting for you at the Meeting Point in the Arrival Hall. The bus driver will arrive 10 minutes before the time of the meeting and will check for each participant on his or her list. There may be delays in case of poor weather.  The bus will drop you in front of or close to your hotel. If you miss the bus initially booked, you can get the next one. If you miss the last transfer, taking a taxi will be the only solution (warning, about 250 Euros!!!)

The registration will start on Monday January 6th at 8am, the conference will start at 8.45am. The conference will take place at the Majestic Congress Center, located 241 Allée du Majestic, in downtown Chamonix. There are signs all over town directing to Majestic Congrés. (No skiing equipment, i.e., skis, boots, boards, is allowed inside the building.) Speakers are advised to check with their chair in advance about downloading their talk.

The Richard Tweedie ski race should take place on Wednesday at 1pm, weather and snow permitting. There will be a registration line at the registration desk. (The cost is 10€ per person and does not include lift passes or equipment.) Thanks to Antonietta Mira, there will be two pairs of skis to be won!)

## MCMSki IV, Jan. 6-8, 2014, Chamonix (news #16)

Posted in Mountains, R, Statistics, University life with tags , , , , , , , , , , , on December 31, 2013 by xi'an

I am now in Chamonix, a week before MCMSki IV. The town is packed with tourists from all over Europe, English being the dominant language. There is not much snow so far, even though some runs reach town. (I did ski in the nearby Les Houches today and the red runs were either icy or very thin, with stones and grass showing here and there…) Since the town is quite pricey in comparison with other French ski resorts, esp. in terms of rental, let me point out the special store of Technique Extrême, with very low rates, located a few blocks away from the conference centre. I am currently trying to see whether or not we could get special rates for the daily passes. I checked whether ski passes could be sold at the registration desk, but the only solution was for me to buy them in advance, so I gave up on that. If you arrive on Sunday my advice is to buy the pass from one of the cablecar stations (which close about 5pm). You can also buy it on line. And pick it later from a cablecar station booth…

## MCMSki IV, Jan. 6-8, 2014, Chamonix (news #15)

Posted in Mountains, R, Statistics, University life with tags , , , , , , , , , , , on December 26, 2013 by xi'an

The programs of the talks, posters and workshop are now printed and available on Speaker Deck (talks, posters, workshop). Please let me know if you spot anything wrong (even though it will not be reprinted!). This is presumably the last news item till Jan. 5 as I am almost off to Chamonix for a week of hard work preparing the conference happily skiing with my family, looking forward seeing some participants in the coming week in the streets of Chamonix and all of them/you on Monday, Jan. 6, 8:30! (Snow is falling right now, so there should be no issue with finding open runs…)

## MCMSki IV, Jan. 6-8, 2014, Chamonix (news #14)

Posted in Mountains, R, Statistics, University life with tags , , , , , , , , , , , , on December 22, 2013 by xi'an

We are quite glad to announce that, thanks to the support of several publishers (CRC Press/Taylor & Francis, Elsevier, and Springer-Verlag), there will be book prizes for both poster nights at MCMSki IV ! I was reminded of this possibility during O-Bayes 2013 and those publishers reacted both quickly and positively to my request (and so did the members of the juries). The list and abstracts of the 75 posters are available on the special blog. (It will not necessarily be provided on site so make sure to store it and bring it with you!)

Another thing of importance: if you have not booked your shuttle through the registration webpage, you have to find a private shuttle on your own. The doodles I set to monitor arrivals and departures did not fill up well enough to be of use. Once again, do not rely on taxis! Looking forward seeing the 200+ participants on January 06 in Chamonix, best Season Wishes!

And even though this is only of interest to locals, Nicolas and Robin have planned an “MCMSki decompression session” at the BiP seminar on 23rd January: MCMSki attendees will give a short presentation of a talk that they liked (or disliked?). Something to keep in mind during the conference. (Guest posts for the ‘Og are also invited from all participants.)

## O’Bayes 2013

Posted in Statistics, Travel, University life, Wines with tags , , , , , , , on December 17, 2013 by xi'an

It was quite sad that we had to start the O-Bayes 2103 conference with the news that Dennis Lindley passed away, but the meeting is the best opportunity to share memories and stress his impact on the field. This is what happened yesterday in and around the talks. The conference(s) is/are very well-attended, with 200-some participants in total, and many young researchers. As in the earlier meetings, the talks are a mixture of “classical” objective Bayes and non-parametric Bayes (my own feeling being of a very fuzzy boundary between both perspectives, both relying to some extent on asymptotics for validation). I enjoyed in particular Jayanta’s Ghosh talk on the construction of divergence measures for reference priors that would necessarily lead to the Jeffreys prior. With the side open problem of determining whether there are only three functional distances (Hellinger, Kullback and L1 that are independent of the dominating measure. (Upon reflection, I am not sure about this question and whether I got it correctly, as one can always use the prior π as the dominating measure and look at divergences of the form

$J(\pi) = \int d\left(\dfrac{\text{d}\pi(\cdot|x)}{\text{d}\pi(\cdot)}\right) m(x)\text{d}x$

which seems to open up the range of possible d’s…) However, and in the great tradition of Bayesian meetings, the best part of the day was the poster session. From enjoying a (local) beer with old friends to discussing points and details.  (It is just unfortunate that by 8:15 I was simply sleeping on my feet and could not complete my round of O’Bayes posters, not even mentioning EFaB posters that sounded equally attractive… I even missed discussing around a capture-recapture poster!)