Publications by xi'an
meandering
A bit of a misunderstanding from Randall Munroe and then some: the function F returns a triplet, hence G should return a triplet as well. Even if the limit does return three identical values. And he should have also included the (infamous) harmonic mean! And the subtext (behind the picture) mentions random forest statistics, using every mean one ...
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handbook of mixture analysis [review]
“In my opinion, the editors have done an excellent job when selecting the contents of the handbook and putting the different chapters together. For instance, this can be appreciated by the fact that, despite the large number of authors and contributions, all chapters have kept the same notation. Furthermore, in addition to a sound description o...
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composition versus inversion
While trying to convey to an OP on X validated why the inversion method was not always the panacea in pseudo-random generation, I took the example of a mixture of K exponential distributions when K is very large, in order to impress (?) upon said OP that solving F(x)=u for such a closed-form cdf F was very costly even when using a state-of-the-ar...
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plusquamperfect squares
A perfect riddle: For some perfect squares, when you remove the last digit, you get another perfect square. The first five perfect squares are 16, 49, 169, 256 and 361. What are the next three ones? Is there a more than perfect square other than 169 such that removing the last two digits returns a perfect square? Writing an R code for plusquamp...
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ABC in Svalbard [#1]
It started a bit awkwardly for me as I ran late, having accidentally switched to UK time the previous evening (despite a record-breaking biking-time to the University!), then the welcome desk could not find the key to the webinar room and I ended up following the first session from my office, by myself (and my teapot)… Until we managed to reuni...
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ABC in Svalbard [#2]
The second day of the ABC wwworkshop got a better start than yesterday [for me] as I managed to bike to Dauphine early enough to watch the end of Gael’s talk and Matias Quiroz’ in full on the Australian side (of zoom). With an interesting take on using frequency-domain (pseudo-)likelihoods in complex models. Followed by two talks by David Fra...
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the new DIYABC-RF
My friends and co-authors from Montpellier have released last month the third version of the DIYABC software, DIYABC-RF, which includes and promotes the use of random forests for parameter inference and model selection, in connection with Louis Raynal’s thesis. Intended as the earlier versions of DIYABC for population genetic applications. Bien...
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ABC in Svalbard [the day after]
The following and very kind email was sent to me the day after the workshop thanks once again to make the conference possible. It was full of interesting studies within a friendly environment, I really enjoyed it. I think it is not easy to make a comfortable and inspiring conference in a remote version and across two continents, but this has bee...
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simulating Maxwell distribution
A question that came out on X validated a few days ago is how to efficiently simulate from a distribution with density x²φ(x). (Obviously properly normalised since the second moment of the standard Normal distribution is one.) The first solution that came out (by Jarle Tufto) exploits the fact that this density corresponds to a signed root of...
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ten computer codes that transformed science
In a “Feature” article of 21 January 2021, Nature goes over a poll on “software tools that have had a big impact on the world of science”. Among those, the Fortran compiler (1957), which is one of the first symbolic languages, developed by IBM. This is the first computer language I learned (in 1982) and one of the two (with SAS) I ever co...
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