Archive for October, 2012

yet another sunrise, on ISU campus

Posted in pictures, Running, Travel with tags , , , , on October 31, 2012 by xi'an

visit to ISU

Posted in pictures, R, Running, Statistics, Travel, University life with tags , , on October 31, 2012 by xi'an

 

A short visit to ISU but and therefore a busy and proftable day! About ten appointments in Snedecor Hall after a nice morning run, a highly attended Zyskind Lecture, and many interesting discussions all over the day: e.g., I had a great time discussing using null recurrent Markov chains for integral approximations with Krishna Athreya and Vivek Roy, following Vivek’s seminar last week, ABC for spatial point processes with Alicia Carriquiry and Kristian Schmidt, SMC and ABC with [fellow blogger] Jarad Niemi, empirical likelihood with Song Chen, and hierarchical Bayes modelling and model checking with Mark Kaiser. I also met an impressive PhD student, Yihui Xie, who seems to have an endless pool of energy as he develops R packages by the dozen, such as animation, formatR, and knitr such as animation, formatR, and knitr, the later being an alternative to sweave, works on a book and seems to be contributing a lot to community sites like RPubs, in addition to maintaining his own blog… I actually took the opportunity to ask him a problem that bugged me for a while, namely how to include R code within beamer so that when I give a class/talk I can click on the code and see the output coming on the slide…

another sunrise in Iowa at ISU

Posted in pictures, Running, Travel with tags , , , , on October 30, 2012 by xi'an

the anti-Bayesian moment and its passing

Posted in Books, Statistics, University life with tags , , , , , , , , on October 30, 2012 by xi'an

Today, our reply to the discussion of our American Statistician paper “Not only defended but also applied” by Stephen Fienberg, Wes Johnson, Deborah Mayo, and Stephen Stiegler,, was posted on arXiv. It is kind of funny that this happens the day I am visiting Iowa State University Statistics Department, a department that was formerly a Fisherian and thus anti-Bayesian stronghold. (Not any longer, to be sure! I was also surprised to discover that before the creation of the department, Henry Wallace, came to lecture on machine calculations for statistical methods…in 1924!)

The reply to the discussion was rewritten and much broadened by Andrew after I drafted a more classical point-by-point reply to our four discussants, much to its improvement. For one thing, it reads well on its own, as the discussions are not yet available on-line. For another, it gives a broader impact of the discussion, which suits well the readership of The American Statistician. (Some of my draft reply is recycled in this post.)

Continue reading

sunrise in Des Moines

Posted in pictures, Running, Travel with tags , , , on October 29, 2012 by xi'an

 

ABC in Le Monde?

Posted in Books, pictures, Statistics, Travel, University life, Wines with tags , , , , , , , , , , on October 29, 2012 by xi'an

In the plane to Chicago, while being stuck on the tarmac at Roissy airport for an hour, I went through my newspapers, only to have the pleasant surprise find in the science leaflet of Le Monde that my co-author Arnaud Estoup, senior researcher at INRA in Montpellier (CBGP), was mentioned in a full page article for his work on the multi-colored Asian lady beetle (Harmonia axyridis, HA), establishing “that the recent burst of worldwide invasions of HA followed a bridgehead scenario, in which an invasive population in eastern North America acted as the source of the colonists that invaded the European, South American and African continents, with some admixture with a biocontrol strain in Europe“. Obviously, Le Monde does not goes as far as mentioning ABC, which was used in our paper to compare scenarios, i.e. to make ABC model choice! (I may also add that the invasion of those Asian bettles in our neighbourhood is a real nuisance and, each Fall, I keep checking for any sign of black beetles inside the house before disaster strikes…)

Despite an inauspicious start (RER B train finishing its trip in Paris and forcing me to board in a hurry a taxi to the airport, abyssal mess at Roissy airport [now, that's a surprise!], departure delayed by 90 minutes), I got some work done during the nine hour flight, including reading and reviewing a PhD thesis, and I even managed to get my connection from Chicago to Des Moines despite a tight 45 minutes transfer time! At a personal level, this reminded me of the very first time I flew to the US, in August 1987, as it also was through O’Hare and I also had to rush to get my connection to Lafayette, Indiana. Even more anecdotally, this AF0664 flight from Paris to Chicago happened to be the very last one, as the route is discontinued by Air France. The second flight to Des Moines was on a small propeller plane and, despite sitting next to an obnoxious drunk woman who wanted me to know everything about her [dull, so very dull] life, quite pleasant: I finished reading in the Midwest sun the highly entertaining thriller by Cédric Villani, Le Théorème vivant. (Obviously soon to be reviewed on The ‘Og!)

the large half now

Posted in R, Statistics with tags , , , on October 28, 2012 by xi'an

The little half puzzle proposed a “dumb’ solution in that players play a minimax strategy. There are 34 starting values less than 100 guaranteeing a sure win to dumb players. If instead the players maximise their choice at each step, the R code looks like this:

solveO=function(n){
if (n<3){ solve=(n==2)}else{
  solve=(!(solveO(n-1)))||(!solveO(ceiling(n/2)))}
solve}

and there are now 66 (=100-34, indeed!) starting values for which the starting player can win.

Incidentally, I typed

> solveO(1113)
Error: evaluation nested too deeply: infinite recursion / options(expressions=)?

which shows R cannot handle heavy recursion without further programming. Testing for the upper limit, I found that the largest acceptable value is 555 (which takes forever to return a value, predicted at more than one hour by a linear regression on the run times till 300…).

Follow

Get every new post delivered to your Inbox.

Join 667 other followers