Publications by xi'an
Bounded target support
Here is an interesting question from Tomàs that echoes a lot of related emails: I’m turning to you for advice. I’m facing problem where parameter space is bounded, e.g. all parameters have to be positive. If in MCMC as proposal distribution I use normal distribution, then at some iterations I get negative proposals. So my question is: sho...
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The foundations of Statistics: a simulation-based approach
“We have seen that a perfect correlation is perfectly linear, so an imperfect correlation will be `imperfectly linear’.” page 128 This book has been written by two linguists, Shravan Vasishth and Michael Broe, in order to teach statistics “in areas that are traditionally not mathematically demanding” at a deeper level than traditiona...
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About Fig. 4 of Fagundes et al. (2007)
Yesterday, we had a meeting of our EMILE network on statistics for population genetics (in Montpellier) and we were discussing our respective recent advances in ABC model choice. One of our colleagues mentioned the constant request (from referees) to include the post-ABC processing devised by Fagundes et al. in their 2007 ABC paper. (This paper c...
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Accepted lack of confidence
I just got the following email from PNAS about our Lack of confidence in ABC model choice. Editor's Remarks to Author: both referees now find the manuscript acceptable for publication as do I. Each suggests small changes which I encourage the authors to make prior to having the manuscript go into production. Congratulations on an interesting...
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The foundations of Statistics [reply]
Shravan Vasishth has written a response to my review both published on the Statistics Forum. His response is quite straightforward and honest. In particular, he acknowledges not being a statistician and that he “should spend more time studying statistics”. I also understand the authors’ frustration at trying “to recruit several statistici...
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Le Monde puzzle [#28]
The puzzle of last weekend in Le Monde was about finding the absolute rank of x9 when given the relative ranks of x1,….,x8 and the possibility to ask for relative ranks of three numbers at a time. In R terms, this means being able to use > rank(x[-9]) [1] 1 7 4 6 8 3 2 5 > rank(x[1:3]) [1] 1 3 2 or yet being able to sort the first 8 components...
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Ternary sorting
The last Le Monde puzzle made me wonder about the ternary version of the sorting algorithms, which all seem to be binary (compare x and y, then…). The problem is, given (only) a blackbox procedure that returns the relative order of three arbitrary numbers, how many steps are necessary to sort a series of n nnumbers? The heapsort entry in Wikipe...
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Bayesian Core and loose logs
Jean-Michel (aka Jean-Claude!) Marin came for a few days so that we could make late progress on the revision of our book Bayesian Core towards an Use R! version. In one of the R programs in the mixture chapter, we were getting improbable answers, until we found an R mistake in the shape of > sum(c(1,2,3,log=TRUE)) [1] 7 > sum(c(1,2,3),log=TRUE...
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A slice of infinity
Peng Yu sent me an email about the conditions for convergence of a Gibbs sampler: The following statement mentions convergence. But I’m not familiar what the regularity condition is. “But it is necessary to have a finite probability of moving away from the current state at all times in order to satisfy the regularity conditions on which th...
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Core not in CiRM
Despite not enjoying this year the optimal environment of CiRM, we are still making good progress on the revision (or the R vision) of Bayesian Core. In the past two days, we went over Chapters 1 (Introduction), 2 (Normal Models), 5 (Capture-Recapture Experiments), and 6 (Mixture Models), with Chapters 3 (Regression), 4 (Generalised Linear Models...
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