Articles by xi'an

Le Monde puzzle [#887bis]

November 15, 2014 | xi'an

As mentioned in the previous post, an alternative consists in filling the permutation of {1,…,N} by adding squares left and right until the permutation is complete or no solution is available. While this sounds like the dual of the initial solution, it brings a considerable increase in computing time, as ...
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Le Monde puzzle [#887]

November 14, 2014 | xi'an

A simple combinatorics Le Monde mathematical puzzle: N is a golden number if the sequence {1,2,…,N} can be reordered so that the sum of any consecutive pair is a perfect square. What are the golden numbers between 1 and 25? Indeed, from an R programming point of view, all I have to ...
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Rasmus’ socks fit perfectly!

November 10, 2014 | xi'an

Following the previous post on Rasmus’ socks, I took the opportunity of a survey on ABC I am currently completing to compare the outcome of his R code with my analytical derivation. After one quick correction [by Rasmus] of a wrong representation of the Negative Binomial mean-variance parametrisation [by me], ... [Read more...]

reliable ABC model choice via random forests

October 28, 2014 | xi'an

After a somewhat prolonged labour (!), we have at last completed our paper on ABC model choice with random forests and submitted it to PNAS for possible publication. While the paper is entirely methodological, the primary domain of application of ABC model choice methods remains population genetics and the diffusion of ...
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a bootstrap likelihood approach to Bayesian computation

October 15, 2014 | xi'an

This paper by Weixuan Zhu, Juan Miguel Marín [from Carlos III in Madrid, not to be confused with Jean-Michel Marin, from Montpellier!], and Fabrizio Leisen proposes an alternative to our 2013 PNAS paper with Kerrie Mengersen and Pierre Pudlo on empirical likelihood ABC, or BCel. The alternative is based on ...
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randomness in coin tosses and last digits of prime numbers

October 7, 2014 | xi'an

A rather intriguing note that was arXived last week: it is essentially one page long and it compares the power law of the frequency range for the Bernoulli experiment with the power law of the frequency range for the distribution of the last digits of the first 10,000 prime numbers to ... [Read more...]

The winds of Winter [Bayesian prediction]

October 6, 2014 | xi'an

A surprising entry on arXiv this morning: Richard Vale (from Christchurch, NZ) has posted a paper about the characters appearing in the yet hypothetical next volume of George R.R. Martin’s Song of ice and fire series, The winds of Winter [not even put for pre-sale on amazon!]. Using ... [Read more...]

future of computational statistics

September 28, 2014 | xi'an

I am currently preparing a survey paper on the present state of computational statistics, reflecting on the massive evolution of the field since my early Monte Carlo simulations on an Apple //e, which would take a few days to return a curve of approximate expected squared error losses… It seems ... [Read more...]

a weird beamer feature…

September 23, 2014 | xi'an

As I was preparing my slides for my third year undergraduate stat course, I got a weird error that got a search on the Web to unravel: which was related with a fragile environment but not directly the verbatim part: the reason for the bug was that the end{frame} ... [Read more...]

new kids on the block

September 21, 2014 | xi'an

This summer, for the first time, I took three Dauphine undergraduate students into research projects thinking they had had enough R training (with me!) and several stats classes to undertake such projects. In all cases, the concept was pre-defined and “all they had to do” was running a massive flow ... [Read more...]

STEM forums

August 14, 2014 | xi'an

When visiting the exhibition hall at JSM 2014, I spoke with people from STEM forums on the Springer booth. The concept of STEM (why STEM? Nothing to do with STAN! Nor directly with Biology. It stands as the accronym for Science, Technology, Engineering, and Mathematics.) is to create a sort of ... [Read more...]

new laptop with ubuntu 14.04

August 13, 2014 | xi'an

As I was getting worried about the chances of survival of my current laptop (bought in emergency upon my return from Kyoto!), I decided to use some available grant money to buy a new laptop without stepping through the emergency square. Thanks to my local computer engineer, Thomas, I found ... [Read more...]

ABC model choice by random forests [guest post]

August 10, 2014 | xi'an

[Dennis Prangle sent me his comments on our ABC model choice by random forests paper. Here they are! And I appreciate very much contributors commenting on my paper or others, so please feel free to join.] This paper proposes a new approach to likelihood-free model choice based on random forest ... [Read more...]

another R new trick [new for me!]

July 15, 2014 | xi'an

While working with Andrew and a student from Dauphine on importance sampling, we wanted to assess the distribution of the resulting sample via the Kolmogorov-Smirnov measure where F is the target.  This distance (times √n) has an asymptotic distribution that does not depend on n, called the Kolmogorov distribution. After ... [Read more...]

implementing reproducible research [short book review]

July 14, 2014 | xi'an

As promised, I got back to this book, Implementing reproducible research (after the pigeons had their say). I looked at it this morning while monitoring my students taking their last-chance R exam (definitely last chance as my undergraduate R course is not reconoduced next year). The book is in fact ... [Read more...]

Le Monde puzzle [#875]

July 11, 2014 | xi'an

I learned something in R today thanks to Le Monde mathematical puzzle: A two-player game consists in A picking a number n between 1 and 10 and B and A successively choosing and applying one of three transforms to the current value of n n=n+1, n=3n, n=4n, starting with ...
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