Archive for TOMACS

Posterior expectation of regularly paved random histograms

Posted in Books, Statistics, University life with tags , , , , , , , , , on October 7, 2013 by xi'an

Today, Raazesh Sainudiin from the University of Canterbury, in Christchurch, New Zealand, gave a seminar at CREST in our BIP (Bayesians in Paris) seminar series. Here is his abstract:

We present a novel method for averaging a sequence of histogram states visited by a Metropolis-Hastings Markov chain whose stationary distribution is the posterior distribution over a dense space of tree-based histograms. The computational efficiency of our posterior mean histogram estimate relies on a statistical data-structure that is sufficient for non-parametric density estimation of massive, multi-dimensional metric data. This data-structure is formalized as statistical regular paving (SRP). A regular paving (RP) is a binary tree obtained by selectively bisecting boxes along their first widest side. SRP augments RP by mutably caching the recursively computable sufficient statistics of the data. The base Markov chain used to propose moves for the Metropolis-Hastings chain is a random walk that data-adaptively prunes and grows the SRP histogram tree. We use a prior distribution based on Catalan numbers and detect convergence heuristically. The L1-consistency of the the initializing strategy over SRP histograms using a data-driven randomized priority queue based on a generalized statistically equivalent blocks principle is proved by bounding the Vapnik-Chervonenkis shatter coefficients of the class of SRP histogram partitions. The performance of our posterior mean SRP histogram is empirically assessed for large sample sizes simulated from several multivariate distributions that belong to the space of SRP histograms.

The paper actually appeared in the special issue of TOMACS Arnaud Doucet and I edited last year. It is coauthored by Dominic Lee, Jennifer Harlow and Gloria Teng. Unfortunately, Raazesh could not connect to our video-projector. Or fortunately as he gave a blackboard talk that turned to be fairly intuitive and interactive.

back from down under

Posted in Books, pictures, R, Statistics, Travel, University life with tags , , , , , , , , , , , , , , on August 30, 2012 by xi'an

After a sunny weekend to unpack and unwind, I am now back to my normal schedule, on my way to Paris-Dauphine for an R (second-chance) exam. Except for confusing my turn signal for my wiper, thanks to two weeks of intensive driving in four Australian states!, things are thus back to “normal”, meaning that I have enough of a control of my time to handle both daily chores like the R exam and long-term projects. Including the special issues of Statistical Science, TOMACS, and CHANCE (reviewing all books of George Casella in memoriam). And the organisation of MCMSki 4, definitely taking place in Chamonix on January 6-8, 2014, hopefully under the sponsorship of the newly created BayesComp section of ISBA. And enough broadband to check my usual sites and to blog ad nauseam.

This trip to Australia, along the AMSI Lectures as well as the longer visits to Monash and QUT, has been quite an exciting time, with many people met and ideas discussed. I came back with a (highly positive) impression of Australian universities as very active places, just along my impression of Australia being a very dynamic and thriving country, far far away from the European recession. I was particularly impressed by the number of students within Kerrie Mengersen’s BRAG group, when we did held discussions in classrooms that felt full like a regular undergrad class! Those discussions and meetings set me towards a few new projects along the themes of mixture estimation and model choice, as well as convergence assessment. During this trip, I however also felt the lack of long “free times” I have gotten used to, thanks to the IUF chair support, where I can pursue a given problem for a few hours without interruption. Which means that I did not work as much as I wanted to during this tour and will certainly avoid such multiple-step trips in a near future. Nonetheless, overall, the own under” experience was quite worth it! (Even without considering the two weeks of vacations I squeezed in the middle.)

Back to “normal” also means I already had two long delays caused by suicides on my train line…

Special issue of TOMACS

Posted in Books, R, Statistics, University life with tags , , , , , on March 10, 2011 by xi'an

TOMACS (ACM Transactions on Modeling and Computer Simulation) is launching a call for paper submission. The special topic is Monte Carlo Methods in Statistics and Arnaud Doucet and myself are the special issue editors. Here are the details.:

Over the last two decades Monte Carlo methods have attracted much attention from statisticians as they provide enormous scope for realistic statistical modeling. This is a very active research field with recent developments including adaptive Markov chain Monte Carlo methods, population Monte Carlo methods and approximate Bayesian computation among others. The recent introduction of Graphics Processing Units shows also great promise and open new research
directions.

The purpose of this special issue of TOMACS is to propose a selection of high quality papers reporting the latest research covering the methodology and implementation of recent developments in Monte Carlo methodology for statistics. Topics include but are not limited to:

  • Markov chain Monte Carlo
  • Sequential Monte Carlo
  • Stochastic approximation
  • Approximate Bayesian computation and other approximations
  • Massive parallelization for high-dimensional problems

The submission deadline is October 30, 2011. The special issue should appear in early 2012. For the editorial policy, instructions to authors, and further details, please consult the ACM TOMACS Web page.

The submission process is electronic only. When submitting your paper, select the appropriate special issue, on Monte Carlo Methods in Statistics, and make sure that you carefully follow the instructions.

We are thus looking forwards your submissions!

ACM Transactions on Modeling and Computer Simulation

Posted in Books, R, Statistics, University life with tags , , , on May 21, 2010 by xi'an

Pierre Lecuyer is the new editor of the ACM Transactions on Modeling and Computer Simulation (TOMACS) and he has asked me to become an Area Editor for the new area of simulation in Statistics. I am quite excited by this new Æditor’s hat, since this is a cross-disciplinary journal:

The ACM Transactions on Modeling and Computer Simulation (TOMACS) provides a single archival source for the publication of high-quality research and developmental results in computer simulation. The subjects of emphasis are discrete event simulation, combined discrete and continuous simulation, as well as Monte Carlo methods. Papers in continuous simulation will also receive serious consideration if their contributions to modeling and simulation in general are substantial.

The use of simulation techniques is pervasive, extending to virtually all the sciences. TOMACS serves to enhance the understanding, improve the practice, and increase the utilization of computer simulation. Submissions should contribute to the realization of these objectives, and papers treating applications should stress their contributions vis-a-vis these objectives.

As an indication of this cross-disciplinarity, I note that most Area Editors and Associate Editors are unknown to me (except for Luc Devroye, of course!). In addition, I savour the irony of being associated with a journal of the Association for Computer Machinery (ACM), given my complete lack of practical skills! So, if you have relevant papers to submit in the field, please consider the ACM Transactions on Modeling and Computer Simulation (TOMACS) as a possible outlet.

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