Publications by xi'an
Tools for Online Teaching
Last semester (Fall 2014), I organized and taught an interdisciplinary, collaborative class titled Probability for Scientists. Getting 4 separate teachers on the same page was a challenge, but as scientists we’re used to communicating over email, and CC’ing everyone worked well enough. Throw in a shared dropbox folder, a shared google calend...
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checking for finite variance of importance samplers
Over a welcomed curry yesterday night in Edinburgh I read this 2008 paper by Koopman, Shephard and Creal, testing the assumptions behind importance sampling, which purpose is to check on-line for (in)finite variance in an importance sampler, based on the empirical distribution of the importance weights. To this goal, the authors use the upper tai...
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Statistical modeling and computation [apologies]
In my book review of the recent book by Dirk Kroese and Joshua Chan, Statistical Modeling and Computation, I mistakenly and persistently typed the name of the second author as Joshua Chen. This typo alas made it to the printed and on-line versions of the subsequent CHANCE 27(2) column. I am thus very much sorry for this mistake of mine and most...
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trying to speed up Metropolis… and failing!
A while ago (but still after Iceland since I used the thorn rune as a math symbol!), I wrote the following post draft as a memo. Now that Marco Banterle, Clara Grazian and myself have completed our delayed acceptance paper, it may be of interest to some readers to see how a first attempt proved fruitless. In the past days, I tried to speed up my ...
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revenge of the pigeons
While I had not had kamikaze pigeons hitting my windows for quite a while…, it may be that one of them decided to move to biological warfare: when I came back from Edinburgh, my office at the University was in a terrible state as a bird had entered through a tiny window opening and wrecked havoc on the room, dropping folders and rocks from my s...
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ABC model choice by random forests
After more than a year of collaboration, meetings, simulations, delays, switches, visits, more delays, more simulations, discussions, and a final marathon wrapping day last Friday, Jean-Michel Marin, Pierre Pudlo, and I at last completed our latest collaboration on ABC, with the central arguments that (a) using random forests is a good tool f...
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R/Rmetrics in Paris [alas!]
Today I gave a talk on Bayesian model choice in a fabulous 13th Century former monastery in the Latin Quarter of Paris… It is the Collège des Bernardins, close to Jussieu and Collège de France, unbelievably hidden to the point I was not aware of its existence despite having studied and worked in Jussieu since 1982… I mixed my earlier San An...
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recycling accept-reject rejections (#2)
Following yesterday’s post on Rao’s, Liu’s, and Dunson’s paper on a new approach to intractable normalising constants, and taking advantage of being in Warwick, I tested the method on a toy model, namely the posterior associated with n Student’s t observations with unknown location parameter μ and a flat prior, which is “naturally�...
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Efficient Ragged Arrays in R and Rcpp
When is R Slow, and Why? Computational speed is a common complaint lodged against R. Some recent posts on r-bloggers.com have compared the speed of R with some other programming languages [1], and showed the favorable impact of the new compiler package on run-times [2]. I and others have written about using Rcpp to easily write C++ functions ...
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ABC in Cancún
Here are our slides for the ABC [very] short course Jean-Michel and I give at ISBA 2014 in Cancún next Monday (if your browser can manage Slideshare…) Although I may switch the pictures from Iceland to Mexico, on Sunday, there will be not much change on those slides we both have previously used in previous short courses. (With a few extra slid...
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