Publications by xi'an
di Roma
It has been a wonderful week in Roma, a mix of pleasant work and enjoyable free-time! I gave the ABC advanced course for the second time in a month so it did not require much in terms of preparation and there was a good sized audience with attentive (if too silent!) students and friends as well. The addition of the R labs was a clear bonus and I ...
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IS vs. self-normalised IS
I was grading my Master projects this morning and came upon this graph: which compares the variability of an importance-sampling estimator versus its self-normalised alternative… This is an interesting case in that self-normalisation does considerably degrade the quality of the approximation in that setting. In other cases, self-normalisation m...
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simulated annealing for Sudokus [2]
On Tuesday, Eric Chi and Kenneth Lange arXived a paper on a comparison of numerical techniques for solving sudokus. (The very Kenneth Lange who wrote this fantastic book on numerical analysis.) One of these techniques is the simulated annealing approach I had played with a long while ago. They seem to use the same penalisation function as mine,...
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What are the distributions on the positive k-dimensional quadrant with parametrizable covariance matrix? (bis)
Wondering about the question I posted on Friday (on StackExchange, no satisfactory answer so far!), I looked further at the special case of the gamma distribution I suggested at the end. Starting from the moment conditions, and the solution is (hopefully) given by the system The resolution of this system obviously imposes conditions on those m...
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What are the distributions on the positive k-dimensional quadrant with parametrizable covariance matrix? (solved)
Paulo (from the Instituto de Matemática e Estatística, Universidade de São Paulo, Brazil) has posted an answer to my earlier question both as a comment on the ‘Og and as a solution on StackOverflow (with a much more readable LaTeX output). His solution is based on the observation that the multidimensional log-normal distribution still allows...
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[not] Le Monde puzzle (solution)
Following the question on dinner table permutations on StackExchange (mathematics) and the reply that the right number was six, provided by hardmath, I was looking for a constructive solution how to build the resolvable 2-(20,5,1) covering. A few hours later. hardmath again came up with an answer, found in the paper Equitable Resolvable Covering...
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mad statistic
In the motivating toy example to our ABC model choice paper, we compare summary statistics, mean, median, variance, and… median absolute deviation (mad). The latest is the only one able to discriminate between our normal and Laplace models (as now discussed on Cross Validated!). When rerunning simulations to produce nicer graphical outcomes (fo...
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what’s wrong with package comment?!
I spent most of the Sunday afternoon trying to understand why defining \newcommand{\era}{\end{comment}} did not have the same effect as writing the line \end{comment} until I found there is a clash due to the comment package… The assuredly simple code \documentclass{book} \usepackage{comment} \begin{document} \begin{comment} prompt, you coul...
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relevant, revised, & resubmitted
We have now completed our revision of the paper Relevant statistics for Bayesian model choice, written with Judith Rousseau, Jean-Michel Marin, and Natesh Pillai. It has been resubmitted to Series B and reposted on arXiv. The major change in the paper is the inclusion of a check about the relevance of a given summary statistics, as already explai...
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ASA fellows
Being freshly elected ASA Fellow (yay!), I just received the list of 2012 ASA Fellows. Among whose, let me mention Sudipto Banerjee, University of Minnesota, Minneapolis, Minnesota, elected “For theoretical, methodological and applied research in spatiotemporal statistical modeling, especially as applied to problems in environmetrics, ecology,...
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