Articles by xi'an

CosmoPMC released

January 12, 2011 | xi'an

Martin Kilbinger, an astronomer (cosmologist) with whom we had worked on population Monte Carlo for cosmological inference [during the ANR-05-BLAN-0283- 04 ANR ECOSSTAT grant], has made the PMC C codes available on the CosmoPMC webpage. He has also written a CosmoPMC manual that is now available from arXiv. And ...
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Two short Bayesian courses in South’pton

January 12, 2011 | xi'an

An announcement for two short-courses on Introduction to  Bayesian Analysis and MCMC, and Hierarchical Modelling of Spatial and Temporal Data by Alan Gelfand (Duke University, USA) and Sujit Sahu (University of Southampton, UK), are to take place in Southampton on June 7-10, this year. Course 1: Introduction to Bayesian Analysis and ... [Read more...]

Le Monde puzzle [1]

January 10, 2011 | xi'an

Following the presentation of the first Le Monde puzzle of the year, I tried a simulated annealing solution on an early morning in my hotel room. Here is the R code, which is unfortunately too rudimentary and too slow to be able to tackle n=1000. #minimise \sum_{i=1}^I x_... [Read more...]

Arrogance sampling

January 7, 2011 | xi'an

A new posting on arXiv by Benedict Escoto on a simulation method for approximating normalising constants (i.e. evidence) with an eye-catching name! Here is the abstract This paper describes a method for estimating the marginal likelihood or Bayes factors of Bayesian models using non-parametric importance sampling (“arrogance sampling”). This ... [Read more...]

a survey on ABC

January 6, 2011 | xi'an

With Jean-Michel Marin, Pierre Pudlo and Robin Ryder, we just completed a survey on the ABC methodology. It is now both arXived and submitted to Statistics and Computing. Rather interestingly, our first draft was written in Jean-Michel’s office in Montpelier by collating the ‘Og posts surveying new ABC papers! (...
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Short review of the R book

January 5, 2011 | xi'an

David Scott wrote a review of Introducing Monte Carlo Methods with R in the International Statistical Review that is rather negative, since the main bulk reads as follows: I found some aspects of the book very disappointing. The first chapter (“Basic R Programming”) has some unfortunate mistakes and some statements, ...
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Adap’skiii [day 2]

January 5, 2011 | xi'an

Another exciting day at Adap’skiii!!! Yves Atchadé presented a very recent work on the fundamental issue of estimating the asymptotic variance estimation for adaptive MCMC algorithms, with an intriguing experimental observation that a non-converging bandwidth with rate 1/n was providing better coverage than the converging rate. (I always found ...
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Le Monde puzzle [52|solution]

January 1, 2011 | xi'an

I have now received the first issue of Le Monde magazine, including the solution to puzzle #52 I solved just in time by simulated annealing! The trick is in using the following theorem: Iter(1,x,y) is divisible by 10x-1 if and only if y is divisible by 10x-1. Then the ... [Read more...]

History makes Stat. Science!

December 31, 2010 | xi'an

While the above heading sounds like a title in reverse, its words are in the “correct” order in that our paper with George Casella, A Short History of Markov Chain Monte Carlo, has been accepted for publication by Statistical Science. This publication may sound weird when considering that the paper ... [Read more...]

Le Monde puzzle [52]

December 31, 2010 | xi'an

The last puzzle of the year in Le Monde reads as follows (as far as I understand its wording!): Iter(n,x,y) is the function Iter=function(n,x,y){ if (n==1){ output=trunc(y/10)+x*(y%%10) }else{ output=Iter(n-1,x,Iter(1,x,y))} return output } Find the ... [Read more...]

More typos in Chapter 5

December 29, 2010 | xi'an

Following Ashley’s latest comments on Chapter 5 of Introducing Monte Carlo Methods with R, I realised Example 5.5 was totally off-the-mark! Not only the representation of the likelihood should have used prod instead of mean, not only the constant should call the val argument of integrate, not only integrate  uses lower ...
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nlm [unused argument(s) (iter = 1)]

December 28, 2010 | xi'an

Ashley put the following comment on Chapter 5 of Introducing Monte Carlo Methods with R”: I am reading chapter 5. I try to reproduced the result on page 128. The R codes don’t work on my laptop. When I try to run the following codes on page 128 __ for (i in 1:(nlm(like,... [Read more...]

Poster at MCMSki III

December 28, 2010 | xi'an

Here is the poster presented at MCMSki III next week by Pierre Jacob about our joint paper on parallelisation: Filed under: R, Statistics, Travel Tagged: Adapski, MCMC, MCMSki, Metropolis-Hastings, Monte Carlo Statistical Methods, parallelisation, pos... [Read more...]

Questions on the parallel Rao-Blackwellisation

December 21, 2010 | xi'an

Pierre Jacob and I got this email from a student about our parallel Rao-Blackwellisation paper. Here are some parts of the questions and our answer: Although I understand how the strategy proposed in the paper helps in variance reduction, I do not understand why you set b=1 (mentioned in Section 3.2) ... [Read more...]

Back from Philly

December 20, 2010 | xi'an

The conference in honour of Larry Brown was quite exciting, with lots of old friends gathered in Philadelphia and lots of great talks either recollecting major works of Larry and coauthors or presenting fairly interesting new works. Unsurprisingly, a large chunk of the talks was about admissibility and minimaxity, with ...
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AMIS revised & resubmitted

December 18, 2010 | xi'an

After a thorough revision that removed most of the theoretical attempts at improving our understanding of AMIS convergence, we have now resubmitted the AMIS paper to Scandinavian Journal of Statistics and arXived the new version as well. (I remind the reader that AMIS stands for adaptive mixture importance sampling and ... [Read more...]

Disas-tea-R at dawn

December 16, 2010 | xi'an

This was bound to happen sooner or later, given my addiction to tea and sleepless nights, so I eventually managed to spill a cup of tea over my Mac… I had been working for a few hours in my hotel room in Philadelphia, completing an ABC paper with Jean-Michel Marin ... [Read more...]

Adap’skiii [latest]

December 13, 2010 | xi'an

Just to point out there still is room for more participants to the Adap’skiii workshop! We have now reached 60 participants for this Utah workshop and would welcome more, quite obviously! All participants are also free to present a poster on the evening of the 4th, in the bar. Filed ... [Read more...]

Truly random [again]

December 9, 2010 | xi'an

“The measurement outputs contain at the 99% confidence level 42 new random bits. This is a much stronger statement than passing or not passing statistical tests, which merely indicate that no obvious non-random patterns are present.” arXiv:0911.3427 As often, I bought La Recherche in the station newsagent for the wrong reason! The ... [Read more...]

Bayesian model selection

December 7, 2010 | xi'an

Last week, I received a box of books from the International Statistical Review, for reviewing them. I thus grabbed the one whose title was most appealing to me, namely Bayesian Model Selection and Statistical Modeling by Tomohiro Ando. I am indeed interested in both the nature of testing hypotheses or ... [Read more...]
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