Archive for RER B
la grande course du grand Paris
Posted in pictures, Running, Travel with tags Central European Summer Time, CEST, half-marathon, Paris, Place de la République, recovery, RER A, RER B, road race, Saint-Denis, semi-marathon, Stade de France, Vincennes - Saint-Denis on March 30, 2025 by xi'an
travel woes
Posted in Travel, University life with tags Astérix et Obélix, Birmingham, CDG, De Gaulle airport, French politics, GNP, Jamel Debbouze, mass tourism, Paris, Paris 2024 Olympics, Paris suburbs, public transportation, RER B, SNCF, tourism nuisances, train travel, University of Warwick on April 29, 2024 by xi'an
On my last trip to Warwick, the local (RER) train I boarded broke on its way to the CDG airport, after hitting something in a tunnel just three stops short of the airport, with so much delay and misleading communication that I missed my flight. While a minor issue for me, since I managed to work (and blog) in an airport lounge for most of the day—where I crossed path with Numerobis—, while waiting for the only flight to B’ham, this made me to reflect anew on the very poor state of the transportation network in Paris and its suburbs, with such incidents (power failures, broken rails, vetust engines, stolen cables, idiots on the tracks, &tc., even without mentioning the strikes) more and more the norm. And to wonder at how the ancient and bursting network is going to cope with the incoming flow of visitors attending the Olympics this summer… Actually, when compared with the other cities with a fairly reasonably efficient airport connection I experienced, it remains a mystery to me why the Greater Paris conurbation—whose president, Valérie Pécresse, was apparently deemed the main culprit for our train break by an incensed fellow passenger that morning!—has kept for years postponing the construction of a dedicated rail line between the airport and central Paris, as the unpredictable and uncomfortable suburban train is not delivering the intended message to Paris visitors and their still-growing contribution to the French GNP. But with the growing public opposition to any new infrastructure, incl. trains, this is unlikely to happen!
me no savi [travel madness]
Posted in Statistics with tags De Gaulle airport, Eindhoven, RER B, Safe Anytime-Valid Inference, SAVI, tomatoes, train station, Uber, workshop on June 1, 2022 by xi'an
Today, I left home in the wee hours, after watering my tomatoes!, quite excited to join the Safe, Anytime-Valid Inference (SAVI) workshop in Eindhoven, which was taking place after two years of postponement. I alas did not check the state of the train traffic beforehand and when I reached the train station I found that part of the line to De Gaulle airport was closed, due to some control cables being stolen last night. Things quickly deteriorated as the train management in Gare du Nord was pretty inefficient, meaning that the trains would stop for five minutes at each station, and that there was no rail alternative to reach Roissy. The taxi stand was a complete mess, with no queue whatsoever, and the Parisian taxis kept true to their reputation, by refusing to take people to the airport, asking for outrageous prices (60 euros per passenger), and stopping anywhere. I almost managed to get one but he refused to take me on top of the Swede family I had directed to this stand from the RER train, and this was simply my last opportunity. Über taxis were invisible and I soon realised I could not catch my flight. Later flights were outrageously expensive and there was not train seat whatsoever till the day after, so I gave up and returned home from this trip to nowhere…
approximate Bayesian inference under informative sampling
Posted in Books, Statistics, Travel, University life with tags ABC, approximate Bayesian inference, Bayesian semi-parametrics, Bernstein-von Mises theorem, Biometrika, estimating equations, generalised method of moments, RER B, Ron Gallant, sampling on March 30, 2018 by xi'an
In the first issue of this year Biometrika, I spotted a paper with the above title, written by Wang, Kim, and Yang, and thought it was a particular case of ABC. However, when I read it on a rare metro ride to Dauphine, thanks to my hurting knee!, I got increasingly disappointed as the contents had nothing to do with ABC. The purpose of the paper was to derive a consistent and convergent posterior distribution based on a estimator of the parameter θ that is… consistent and convergent under informative sampling. Using for instance a Normal approximation to the sampling distribution of this estimator. Or to the sampling distribution of the pseudo-score function, S(θ) [which pseudo-normality reminded me of Ron Gallant’s approximations and of my comments on them]. The paper then considers a generalisation to the case of estimating equations, U(θ), which may again enjoy a Normal asymptotic distribution. Involving an object that does not make direct Bayesian sense, namely the posterior of the parameter θ given U(θ)…. (The algorithm proposed to generate from this posterior (8) is also a mystery.) Since the approach requires consistent estimators to start with and aims at reproducing frequentist coverage properties, I am thus at a loss as to why this pseudo-Bayesian framework is adopted.
simulation in Gare du Nord [jatp]
Posted in Statistics with tags ads, COP 21, France, Gare du Nord, jatp, métro, Paris, RER B, simulation on January 30, 2018 by xi'an
Xi'an's Og 