Archive for trail running

dodging bullets, IEDs, and fingerprint detection at SimStat19

Posted in pictures, Statistics, University life with tags , , , , , , , , , , , , , , , , , on September 10, 2019 by xi'an

I attended a fairly interesting forensic science session at SimStat 2019 in Salzburg as it concentrated on evidence and measures of evidence rather than on strict applications of Bayesian methodology to forensic problems. Even though American administrations like the FBI or various police departments were involved. It was a highly coherent session and I had a pleasant discussion with some of the speakers after the session. For instance, my friend Alicia Carriquiry presented an approach to determined from images of bullets whether or not they have been fired from the same gun, leading to an interesting case for a point null hypothesis where the point null makes complete sense. The work has been published in Annals of Applied Statistics and is used in practice. The second talk by Danica Ommen on fiducial forensics on IED, asking whether or not copper wires used in the bombs are the same, which is another point null illustration. Which also set an interesting questioning on the dependence of the alternative prior on the distribution of material chosen as it is supposed to cover all possible origins for the disputed item. But more interestingly this talk launched into a discussion of making decision based on finite samplers and unknown parameters, not that specific to forensics, with a definitely surprising representation of the Bayes factor as an expected likelihood ratio which made me first reminiscent of Aitkin’s (1991) infamous posterior likelihood (!) before it dawned on me this was a form of bridge sampling identity where the likelihood ratio only involved parameters common to both models, making it an expression well-defined under both models. This identity could be generalised to the general case by considering a ratio of integrated likelihoods, the extreme case being the ratio equal to the Bayes factor itself. The following two talks by Larry Tang and Christopher Saunders were also focused on the likelihood ratio and their statistical estimates, debating the coherence of using a score function and presenting a functional ABC algorithm where the prior is a Dirichlet (functional) prior. Thus a definitely relevant session from a Bayesian perspective!

 

über Salzburg [jatp]

Posted in Mountains, pictures, Running, Travel with tags , , , , , , , , on September 5, 2019 by xi'an

trailers versus mountaineers?

Posted in Kids, Mountains, Running, Travel with tags , , , , , , , , , , , on August 31, 2019 by xi'an

A slight altercation in a swimming corridor during lunch put me back into this Le Monde paper I read yesterday about (real?!) mountaineers being annoyed at trailers, especially those currently running the Ultra-Trail du Mont Blanc (UTMB). A lady stopped me from going further for not crawling as this was a “crawl only” lane and started a lengthy tirade that I cut short by moving to another lane. I find such debates pretty absurd and rather hypocritical. When the fundamental goal is mostly to reduce the number of people on the trails, in the mountains, or in the pool by creating categories with those in and those out. This seems an unavoidable human trend that happened several times in mountaineering, from the early days when going above a certain limited was prohibited to those when climbing solo, rope-free, mixed style, without a registered guide or certificate, &tc. base-jumping, was or became taboo. It is annoying to see crowds in the mountains, whether on the Everest final sketch or on the UTMB track, for sure, but by nature these are singular events and the next peak is almost surely free. It is also annoying to find other climbers on one’s chosen route as they will certainly cause delays, but this is the nature of the game and the next route may well be free. I thus find pretty annoying that some claim their rights to enjoy mountains are higher or purer than others, whom they accuse of elitism and ill-placed competition, when themselves are far from free of the same defect.

 

sunrise on Tenjikuyama [jatp]

Posted in Statistics with tags , , , , , , , , , , , on August 27, 2019 by xi'an

à la maison des mathématiciens [Jean Morlet chair, CIRM, Luminy]

Posted in pictures, Travel, University life with tags , , , , , , , , , , , , , on December 6, 2018 by xi'an

on the trail [jatp]

Posted in Mountains, Running, Statistics, Travel, University life with tags , , , , , , , , , , , , , on November 27, 2018 by xi'an

more smoke on the water [jatp]

Posted in Mountains, pictures, Running, Travel, University life with tags , , , , , , , , , , , on November 26, 2018 by xi'an