Articles by xi'an

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 ...
[Read more...]

ABC in Cancún

July 10, 2014 | xi'an

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 ... [Read more...]

Efficient Ragged Arrays in R and Rcpp

July 3, 2014 | xi'an

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 ... [Read more...]

recycling accept-reject rejections (#2)

July 1, 2014 | xi'an

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 ... [Read more...]

R/Rmetrics in Paris [alas!]

June 29, 2014 | xi'an

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 ... [Read more...]

ABC model choice by random forests

June 24, 2014 | xi'an

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 ... [Read more...]

revenge of the pigeons

June 23, 2014 | xi'an

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 ... [Read more...]

trying to speed up Metropolis… and failing!

June 12, 2014 | xi'an

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 ... [Read more...]

Statistical modeling and computation [apologies]

June 11, 2014 | xi'an

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 ... [Read more...]
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