Publications by xi'an
A new series of mishaps
Following the slight difficulties of last week, I had a hard week on the computer front: indeed, on Monday, I received my 2007 macbook from the repair shop, with a new video card, courtesy of Apple. Unfortunately, this started a series of problems. First, the old macbook stopped recognizing the NVIDIA video and, while it worked under VESA, the sy...
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Parallel computation [revised]
We have now completed our revision of the parallel computation paper and hope to send it to JCGS within a few days. As seen on the arXiv version, and given the very positive reviews we received, the changes are minor, mostly focusing on the explanation of the principle and on the argument that it comes essentially free. Pierre also redrew the gra...
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Bertand’s paradox [R details]
Some may have had reservations about the “randomness” of the straws I plotted to illustrate Bertrand’s paradox. As they were all going North-West/South-East. I had actually made an inversion between cbind and rbind in the R code, which explained for this non-random orientation. Above is the corrected version, which sounds “more random” ...
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Looking at the "Curse of Dimensionality" with R, foreach, and lattice
Here are the results of a “Curse of Dimensionality” homework assignment for Terran Lane’s Introduction to Machine Learning class. Pretty pictures, interesting results, and a good exercise in explicit parallelism with R. It’s neat to see distance scaling linearly with standard deviation, and linearly with the Lth-root for an...
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Statistics forum
The ASA is launching a new blog called the Statistics Forum, managed by Andrew Gelman and to which I will periodically contribute items that may induce some amount of discussion within the community, like the first entry by Michael Lavine on testing. (Meaning I will double-post on the Og and on the Statistics Forum, if I can manage the timing rig...
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JCGS 20th anniversary
For its 20th anniversary, JCGS offers free access to papers, including Andrew’s discussion paper Why tables are really much better than graphs. (Another serious ending for an April fool joke!) Incidentally (or rather coincidentally), I received today the great news that our Using parallel computation to improve Independent Metropolis-Hastings b...
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One bicycle for two
Robin showed me a mathematical puzzle today that reminded me of a story my grand-father used to tell. When he was young, he and his cousin were working in the same place and on Sundays they used to visit my great-grand-mother in another village. However, they only had one bicycle between them, so they would share the bicyle by alternating walking...
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Typos sorted, at last!
After posting so many entries about typos in my books (making you wonder how there could be any text left!) and postponing their classification for so long, I decided on Saturday afternoon to collect those entries into a comprehensive pdf document that should be more useful for readers. I incidentally noticed that my book web-page had not been up...
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MCMC with errors
I received this email last week from Ian Langmore, a postdoc in Columbia: I’m looking for literature on a subject and can’t find it: I have a Metropolis sampler where the acceptance probability is evaluated with some error. This error is not simply error in evaluation of the target density. It occurs due to the method by which we appro...
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Le Monde puzzle [#7]
The mathematical puzzle from the weekend edition of Le Monde from a few weeks ago was not too hard to solve by induction but my R code failed miserably! The puzzle was as follows: A calculator is broken in such a way that it starts by exhibiting 0, then pressing 4, 6 or 0 keeps adding this figure to the right of the current number (if not zero), ...
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