Archive for July, 2011

JSM 2011

Posted in Running, Statistics, Travel, University life on July 31, 2011 by xi'an

Following Julien’s example, I am heading to Miami for JSM 2011 and take advantage of the looong if direct flight there to write a first post on attending JSM this year. The difficulty in such a large meeting is indeed in making a choice among the numerous parallel sessions to build a most profitable programme. Without turning it into an impossibility theorem. So [my] Rule #1 is to stick to a session for the whole time slot rather than trying to attend three talks in three different rooms. Rule #2 is to make one own’s programme from the on-line JSM site well in advance, ideally before starting your day. This way there is time to read the abstracts and to make a coherent choice. Rule #3: I would actually be less open-minded than Julien and opt for sessions whose title make sense to me, as 20 minutes is awfully short to grasp a new domain! Plenary sessions and special invited talks are obviously different in that the speaker has a much longer time to present an overview of one’s field and endeavours… Also take the time to read through the list of posters for keywords in your domains of interest: a random walk through the poster hall may have interesting outcomes, but it is more likely that you will miss the poster that was clearly related to your research.

Among the things I have spotted in my programme for this week in Miami, plenary talks by David Cox and Michael Jordan (Monday), Sylvia Richardson (Tuesday), and Michael Newton and Chris Holmes (Wednesday), the Savage Award session on Monday (I am sure Julien will attend! The model assessment session I organised is unfortunately scheduled at exactly the same time…), the SBSS mixer on Wednesday where prizes will be delivered. Enjoy your programme as well!!! (Sorry for the poor presentation, my Internet connection is just as poor!, and… btw avoid Enso on Lincoln Road Mall, drinks are outrageously overpriced! And, julien, running on the beach is fine if you plan it about 6am… This is the only free slot for the day anyway!)

When has Bayesian analysis really made a difference???

Posted in Books, Statistics, Travel, University life with tags , , , , , on July 30, 2011 by xi'an

With Kerrie Mengersen (QUT, Brisbane), we are launching a call for Bayesian “stories”, towards a collective paper/a special issue:

When has Bayesian analysis really made a difference?

Following the publication of “the theory that would not die” by Sharon McGrayne, about how Bayesian analysis contributed to science and the World in general, we [Kerrie Mengersen (QUT, Brisbane) and Christian Robert (Paris-Dauphine)] would like to put together a collection of six-page vignettes that describe real cases in which Bayesian analysis has been the only way to crack a really important problem.
To this end, we are launching a call for one page proposals that address the following questions.

  • What was the big problem to be solved? We mean big.
  • Why was it so difficult to solve statistically?
  • What was the Bayesian resolution?
  • Why couldn’t it be solved by other means? What were the shortcomings of other statistical solutions?
  • What was the overall impact of this Bayesian analysis on the real world?

We will then review those proposals and select the most significant ones towards the production of six page vignettes, aiming them to be published in a special issue or a multiple authored paper of a mainstream statistical journal. The deadline for the submission of a one-page proposal is September 30. It should be sent to Christian P. Robert at bayesianstatistics@gmailcom in pdf format. The final deadline will depend on the journal editor.

Obviously, if you happen to be like me at JSM 2011 this week and have a proposal (or journal!) in mind, feel free to talk to me about this! (I have also been waiting ages for a copy—two, actually—of the theory that would not die towards the dual goals of reading it and writing a review, but both channels failed to deliver.)

More book reviews!

Posted in Books, Statistics, University life with tags , , , on July 30, 2011 by xi'an

Last week Sam Behseta asked me to join the editorial board of CHANCE as the book editor and I frankly see no reason to refuse the offer! First, it means more books to read and review (hence, free material for the ‘Og!). Second, CHANCE is a general audience statistical journal published by the ASA, hence completely reputable!, and parallel to Significance. Third, it is a fairly pleasant way (for me at least, if not uniformly for the authors) to contribute to the society.

Le Monde puzzle [#29]

Posted in R, Statistics with tags , , on July 29, 2011 by xi'an

This week, the puzzle from the weekend edition of Le Monde was easy to state: in the sequence (8+17n), is there a 6th power? a 7th? an 8th? If so, give the first occurrence. So I first wrote an R code for a function testing whether an integer is any power:

ispower=function(x){
ispo=FALSE
logx=log(x)
i=trunc(logx/log(2))
while((i>1)&&(!ispo)){
j=t=trunc(exp(logx/i))
while (t<x) t=j*t
ispo=(x==t)
if (!ispo){
j=t=j+1
while (t<x) t=j*t
ispo=(x==t)}
i=i-1}
list(is=ispo,pow=j)}

(The function returns the highest possible power.) Then I ran the thing over the first million of values of the sequence:

fib=8
for (j in 1:10^6){
fib=fib+17
tes=ispower(fib)
if (tes$is)
print(c(fib,tes$pow,log(fib)/log(tes$pow)))}

only to find that only the powers 2,3,6,10,11,19 were present among the first terms. Continue reading

Core not in CiRM

Posted in Books, R, Statistics, University life with tags , , , , , , on July 28, 2011 by xi'an

Despite not enjoying this year the optimal environment of CiRM, we are still making good progress on the revision (or the R vision) of Bayesian Core. In the past two days, we went over Chapters 1 (Introduction), 2 (Normal Models), 5 (Capture-Recapture Experiments), and 6 (Mixture Models), with Chapters 3 (Regression), 4 (Generalised Linear Models) and 9 (Image Analysis) being close to completion. While having a “last”go at the R tutorial part of Chapter 1, I came across this paragraph

One of the most frustrating features of R is that the graphical device is not refreshed while a program is executed in the main window. This implies that, if you switch from one terminal to another or if the screen saver starts, the whole or parts of the graph currently on the graphical device will not be visible until the completion of the program. Conversely, refreshing very large graphs will delay the activation of the prompt >.

that I very gladly deleted, as the current 2.11.1 version of R does no longer suffer from this painful freeze in the graphics (at least on my Kubuntu 10.10 version).

Actually, I do not think I mentioned it in a previous post: our new edition will be called Bayesian Essentials with R. Both to distinguish it from Bayesian Core (as it should be published in the Use R! series) and because it appeared (thanks to colleagues and readers) that core did not sound very appealing to English-speaking audiences looking for a statistics book…

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