Archive for Lyon

le grand amphithéâtre de l’Université de Lyon

Posted in Kids, pictures, Travel, University life with tags , , , , , , , , , , on May 5, 2017 by xi'an

The talks of the statlearn 2017 conference took place in an amazing 19th Century amphitheatre that looked in much better conditions than the corresponding amphitheatre of La Sorbonne. After checking on-line, I found that this place had suffered a major fire in 1999 and had been renovated since then.

The main wall features a very academic painting by Jean-Joseph Weerts representing a rhethoric competition in Lugdunum (the hill of the god Lug, in Latin), under the Roman emperor Caligula. (It is hard to imagine this was painted at the time of the Impressionist revolution!) Which creates a huge distraction from listening to the first talk when one enters this room, as there are many stories woven into the painting, including the fate of the poor rethoricians, thrown in the Rhône by the emperor’s guards!

an elegant result on exponential spacings

Posted in Statistics with tags , , , , , , , , , , , , , on April 19, 2017 by xi'an

A question on X validated I spotted in the train back from Lyon got me desperately seeking a reference in Devroye’s Generation Bible despite the abyssal wireless and a group of screeching urchins a few seats away from me… The question is about why

\sum_{i=1}^{n}(Y_i - Y_{(1)}) \sim \text{Gamma}(n-1, 1)

when the Y’s are standard exponentials. Since this reminded me immediately of exponential spacings, thanks to our Devroye fan-club reading group in Warwick,  I tried to download Devroye’s Chapter V and managed after a few aborts (and a significant increase in decibels from the family corner). The result by Sukhatme (1937) is in plain sight as Theorem 2.3 and is quite elegant as it relies on the fact that

\sum_{i=1}^n y_i=\sum_{j=1}^n (n-j+1)(y_{(j)}-y_{(j-1)})=\sum_{j=2}^n (y_{(j)}-y_{(1)})

hence sums up as a mere linear change of variables! (Pandurang Vasudeo Sukhatme (1911–1997) was an Indian statistician who worked on human nutrition and got the Guy Medal of the RSS in 1963.)

ODOF, not Hodor [statlearn 2017]

Posted in Books, Kids, pictures, Statistics, University life with tags , , , , , , , , on April 15, 2017 by xi'an

Fourvière [jatp]

Posted in Mountains, pictures, Running, Travel with tags , , , , , , on April 13, 2017 by xi'an

Saône, sunrise #2 [jatp]

Posted in pictures, Running, Travel, University life with tags , , , , , , , , , , on April 10, 2017 by xi'an

Saône, sunrise [jatp]

Posted in pictures, Running, Travel, University life, Wines with tags , , , , , , , , on April 8, 2017 by xi'an

Statlearn17, Lyon

Posted in Kids, pictures, R, Statistics, Travel, University life with tags , , , , , , , , , , on April 6, 2017 by xi'an

Today and tomorrow, I am attending the Statlearn17 conference in Lyon, France. Which is a workshop with one-hour talks on statistics and machine learning. And which makes for the second workshop on machine learning in two weeks! Yesterday there were two tutorials in R, but I only took the train to Lyon this morning: it will be a pleasant opportunity to run tomorrow through a city I have not truly ever visited, if X’ed so many times driving to the Alps. Interestingly, the trip started in Paris with me sitting in the train next to another speaker at the conference, despite having switched seat and carriage with another passenger! Speaker whom I did not know beforehand and could only identify him by his running R codes at 300km/h.