Archive for Mount Rundle

ABC’ory in Banff [17w5025]

Posted in Books, Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , on February 27, 2017 by xi'an

And another exciting and animated [last] day of ABC’ory [and practice]!  Kyle Cranmer exposed a density ratio density estimation approach I had not seen before [and will comment here soon]. Patrick Muchmore talked about unbiased estimators of Gaussian and non-Gaussian densities in elliptically contoured distributions which allows for running pseudo-MCMC than ABC. This reminded me of using the same tool [for those distributions can be expressed as mixtures of normals] in my PhD thesis, if for completely different purposes. In his talk, including a presentation of an ABC blackbox platform called ELFI, Samuel Kaski did translate statistical inference as inverse reinforcement learning: I hope this does not catch! In the afternoon, Dennis Prangle gave us the intuition behind his rare event ABC, which is not estimating rare events by ABC but rather using rare event simulation to improve ABC. [A paper I will a.s. comment here soon as well!] And Scott Sisson concluded the day and the week with his views on ABC for high dimensions.

While being obviously biased as the organiser of the workshop, I nonetheless feel it was a wonderful meeting with just the right number of participants to induce interactions and discussions during and around the talk, as well as preserve some time for pairwise interactions. Like all other workshops I contributed to in BIRS along the years

07w5079 2007-07-01 Bioinformatics, Genetics and Stochastic Computation: Bridging the Gap
10w2170 2010-09-10 Hierarchical Bayesian Methods in Ecology
14w5125 2014-03-02 Advances in Scalable Bayesian Computation

this is certainly a highly profitable one! For a [major] change, the next one [18w5023] will take place in Oaxaca, Mexico, and will see computational statistics meet molecular simulation. [As an aside, here are the first and last slides of Ewan Cameron’s talk, appropriately illustrating beginning and end, for both themes of his talk: epidemiology and astronomy!]

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snapshot from Banff

Posted in Mountains, pictures, Running, Travel with tags , , , , , , , on September 27, 2015 by xi'an

picture of Vermilon Lake, Banff, Sept. 27, 2015, taken during a nice noon run compensating for the awful morning run in the freezing rain! Too bad I got stung by a bee or a wasp during that run, In the nose. It really hurts!!!

no ISBA 2016 in Banff…

Posted in Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , on July 13, 2014 by xi'an

Banff west-northern range from Rundle, Sept. 10, 2010Alas, thrice alas, the bid we made right after the Banff workshop with Scott Schmidler, and Steve Scott for holding the next World ISBA Conference in 2016 in Banff, Canada was unsuccessful. This is a sad and unforeseen item of news as we thought Banff had a heap of enticing features as a dream location for the next meeting… Although I cannot reveal the location of the winner, I can mention it is much more traditional (in the sense of the Valencia meetings), i.e. much more mare than monti… Since it is in addition organised by friends and in a country I love, I do not feel particularly aggravated. Especially when considering we will not have to organise anything then!

ISBA 2016 in Banff???

Posted in Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , on March 16, 2014 by xi'an

Banff west-northern range from Rundle, Sept. 10, 2010Scott Schmidler, Steve Scott and myself just submitted a proposal for holding the next World ISBA Conference in 2016 in Banff, Canada! After enjoying the superb environment of the Advanced in Scalable Bayesian computation workshop last week, we thought it would be worth a try as a potential location for the next meeting, esp. when considering the superlative infrastructure of the Banff Centre (meaning we really do not have to be local to be local organisers!), the very reasonable rates for renting the site and securing two hundred rooms, the potential for a special collaboration with BIRS, the scarcity of alternative proposals (as far as I can fathom) and the ultimate mountain environment… I remember fondly the IMS annual meeting of 2002 there,  with a great special lecture by Hans Künsch and, exceptionally, an RSS Read Paper by Steve Brooks, Paulo Guidici and Gareth Roberts.  (Not mentioning en exhilarating solo scramble up Mount Temple and another one with Arnaud Guillin up the chimneys of Mount Edith!)  Since the deadline was this Saturday, March 15, we should hear pretty soon if we are successful in this bid. (Good luck to our Scottish friends from Edinburgh for their bid for holding ISBA 2018! Moving from the feet of Mount Rundle [above] to the feet of Arthur’s Seat would make for a great transition.)

Banff workshop [BIRS 12w5105 meeting [#2]]

Posted in Mountains, pictures, Statistics, Travel, University life with tags , , , , , , , , , on March 21, 2012 by xi'an

Today the program of 12w5105 was more on the theoretical side with adaptive MCMC in the morning and ABC in the afternoon. Éric Moulines and Gersende Fort shared a talk on two papers, one on adaptive tempering and the other one on equi-energy sampling, then Nando de Freitas spoke first about Gaussian process approximation for Bayesian optimisation, then about an adaptive Hamiltonian technique called Sardonics. And Jeff Rosenthal concluded the morning with a review of the results ensuring convergence for adaptive MCMC (with a delightful counter-example called Stairways to Heaven that reminded me of an ice climb in Utah!). After my talk, where Scott Sisson made an interesting comment on the difficulty to extend our framework to a large collection of models (since then the summary statistics have to differ), François Perron discussed in highly interesting details several approximation techniques for the Bayesian estimation of copulas and Scott Sisson presented his recent arXiv paper where a rough estimate of the joint posterior is obtained regression-adjustment ABC, and then estimates of each marginal posterior distribution are separately obtained in a lower-dimensional analysis, all this being connected with Bayes linear analysis. (I do not completely get the way summary statistics are selected for each marginal there, which seems to be done by hand. While I understand why using a lower-dimensional statistic helps in improving the approximation of the marginal posteriors and fights the curse of dimensionality, the fact that the joint posterior sample is based on different summary statistics for the different components makes an interesting statistical puzzle. Maybe the copula approach by François in the previous talk could be used at the final stage.) The final talk by Zhiqiang Tan on comparative performances of resampling and subsampling strategies generated a very animated discussion. (All talks being recorded, mine is available as an mp4 video but watch at your own peril!)