## Medellin

Posted in Kids, pictures, Travel with tags , , , , , , , on June 15, 2021 by xi'an

My nephew Paul and a fellow student made this nice mute video as a final project of his cinema degree in Rennes:

## congrats!

Posted in Kids, pictures with tags , , , , , , , on June 14, 2021 by xi'an

This week, our daughter is taking her final exams of her medical studies! Which means competing for the residency specialties and locations at a national level, since the ranking in this competition fully determines the order in selecting one’s residency and hence specialty. Over the past six years, she went though semester exams that were more standard, as well as over thirty externships (as above in the emergency ward at Bicêtre), hence qualified to be a doctor, but this competition is somewhat the most important for medical students who are not considering general practice as a first choice… (In the past years, the least popular specialties were psychiatry, epidemiology, and occupational medicine.) Hence, a particularly stressful moment for them, for which they have been insanely preparing for the past three years. Whatever the outcome of the competition happens to be, congrats to our daughter and her friends for the hard work and the dedication they demonstrated throughout the years, despite the demands imposed by the COVID crisis and despite the absurd features of medical studies in France..!

## journal of the [second] plague year [away]

Posted in Books, Kids, Mountains, pictures, Travel, University life, Wines with tags , , , , , , , , , , , , , , , on June 12, 2021 by xi'an

Read Fred Vargas’s Seeking Whom He May Devour (L’Homme à l’envers), which I found on a bookshelf of our vacation rental in Annecy. And got more quickly bored by the story as it is plagued with the same defects as the ones I read before, from a definitive issue with Canadians (!), to an attempt to bring supernatural causes in the story and reveal them as fake by the end of the book, to a collection of implausible and caricaturesque characters surrounded by the usual backcountry morons that would rather fit a Paasilinna novel, and to the incomprehensible intuitions of Inspector Adamsberg. I also went through the sequel to Infomocracy, Null states, albeit this was a real chore as it lacked substance and novelty (the title by itself should have been a warning!).

Watched Night in Paradise (낙원의 밤), another Korean gangster movie, which seems to repeat the trope of bad-guy-on-the-run-meets-lost-girl found in my previously watched Korean Jo-Phil: The Dawning Rage, where the main character, a crooked police officer is radically impacted after failing to save a lost teenager.  (And also in the fascinating The Wild Goose Lake.) The current film is stronger however in creating the bond between the few-words gangster on the run and the reluctant guest Jae-yeon who is on a run of a different magnitude. While the battle scenes are still grand-guignolesque (if very violent) in a Kill Bill spirit, and the gang leaders always caricaturesque, the interplay between the main characters makes Night in Paradise a pretty good film (and explains why it got selected for the Venice Film Festival of 2020). Also went through the appalling Yamakasi by Luc Besson, a macho, demagogical, sexist, simplist, non-story…

## the pillar of shame [04 June 1989]

Posted in Kids, pictures with tags , , , , , , , , , on June 4, 2021 by xi'an

## on approximations of Φ and Φ⁻¹

Posted in Books, Kids, R, Statistics with tags , , , , , , , , , on June 3, 2021 by xi'an

As I was working on a research project with graduate students, I became interested in fast and not necessarily very accurate approximations to the normal cdf Φ and its inverse. Reading through this 2010 paper of Richards et al., using for instance Polya’s

$F_0(x) =\frac{1}{2}(1+\sqrt{1-\exp(-2x^2/\pi)})$

(with another version replacing 2/π with the squared root of π/8) and

$F_2(x)=1/1+\exp(-1.5976x(1+0.04417x^2))$

not to mention a rational faction. All of which are more efficient (in R), if barely, than the resident pnorm() function.

      test replications elapsed relative user.self
3 logistic       100000   0.410    1.000     0.410
2    polya       100000   0.411    1.002     0.411
1 resident       100000   0.455    1.110     0.455


For the inverse cdf, the approximations there are involving numerical inversion except for

$F_0^{-1}(p) =(-\pi/2 \log[1-(2p-1)^2])^{\frac{1}{2}}$

which proves slightly faster than qnorm()

       test replications elapsed relative user.self
2 inv-polya       100000   0.401    1.000     0.401
1  resident       100000   0.450    1.000     0.450