Archive for the Mountains Category

Astrostatistics school

Posted in Mountains, pictures, R, Statistics, Travel, University life with tags , , , , , , , , , , , , , , , , , , , , , on October 17, 2017 by xi'an

What a wonderful week at the Astrostat [Indian] summer school in Autrans! The setting was superb, on the high Vercors plateau overlooking both Grenoble [north] and Valence [west], with the colours of the Fall at their brightest on the foliage of the forests rising on both sides of the valley and a perfect green on the fields at the centre, with sun all along, sharp mornings and warm afternoons worthy of a late Indian summer, too many running trails [turning into X country ski trails in the Winter] to contemplate for a single week [even with three hours of running over two days], many climbing sites on the numerous chalk cliffs all around [but a single afternoon for that, more later in another post!]. And of course a group of participants eager to learn about Bayesian methodology and computational algorithms, from diverse [astronomy, cosmology and more] backgrounds, trainings and countries. I was surprised at the dedication of the participants travelling all the way from Chile, Péru, and Hong Kong for the sole purpose of attending the school. David van Dyk gave the first part of the school on Bayesian concepts and MCMC methods, Roberto Trotta the second part on Bayesian model choice and hierarchical models, and myself a third part on, surprise, surprise!, approximate Bayesian computation. Plus practicals on R.

As it happens Roberto had to cancel his participation and I turned for a session into Christian Roberto, presenting his slides in the most objective possible fashion!, as a significant part covered nested sampling and Savage-Dickey ratios, not exactly my favourites for estimating constants. David joked that he was considering postponing his flight to see me talk about these, but I hope I refrained from engaging into controversy and criticisms… If anything because this was not of interest for the participants. Indeed when I started presenting ABC through what I thought was a pedestrian example, namely Rasmus Baath’s socks, I found that the main concern was not running an MCMC sampler or a substitute ABC algorithm but rather an healthy questioning of the construction of the informative prior in that artificial setting, which made me quite glad I had planned to cover this example rather than an advanced model [as, e.g., one of those covered in the packages abc, abctools, or abcrf]. Because it generated those questions about the prior [why a Negative Binomial? why these hyperparameters? &tc.] and showed how programming ABC turned into a difficult exercise even in this toy setting. And while I wanted to give my usual warning about ABC model choice and argue for random forests as a summary selection tool, I feel I should have focussed instead on another example, as this exercise brings out so clearly the conceptual difficulties with what is taught. Making me quite sorry I had to leave one day earlier. [As did missing an extra run!] Coming back by train through the sunny and grape-covered slopes of Burgundy hills was an extra reward [and no one in the train commented about the local cheese travelling in my bag!]


Autrans, Vercors [jatp]

Posted in Mountains, pictures, Running, Travel with tags , , , , , , , on October 16, 2017 by xi'an

Gorges de la Bourne [jatp]

Posted in Mountains, pictures, Running, Travel with tags , , , , , , , , on October 12, 2017 by xi'an

[Astrostat summer school] fogrise [jatp]

Posted in Kids, Mountains, pictures, Running, Statistics, Travel, University life with tags , , , , , , , , , on October 11, 2017 by xi'an

[summer Astrostat school] room with a view [jatp]

Posted in Mountains, pictures, R, Running, Statistics, Travel, University life with tags , , , , , , , , , , on October 9, 2017 by xi'an

I just arrived in Autrans, on the Plateau du Vercors overlooking Grenoble and the view is fabulistic! Trees have started to turn red and yellow, the weather is very mild, and my duties are restricted to teaching ABC to a group of enthusiastic astronomers and cosmologists..! Second advanced course on ABC in the mountains this year, hard to beat (except by a third course). The surroundings are so serene and peaceful that I even conceded to install RStudio for my course! Instead of sticking to my favourite vim editor and line commands.

Adam Ondra completes a first 9c

Posted in Kids, Mountains, pictures with tags , , , , , , on September 30, 2017 by xi'an

In my office hangs this poster of Adam Ondra climbing at sunset an impressive overhang with a little Czech town at the foot of the cliff, already in the shade. Impressive because of the view and of the climb which at 7c is a whole grade (and then some) beyond my reach. But now Ondra has managed to climb the first 9c in the world, which is universes beyond the impressive and beyond the fathomable, with passages only manageable feet first. Which actually makes a lot of sense, the way he explains it. The route is currently called Project Hard and is located in Hanshelleren Cave, Flatanger, Norway.

wet summer reads [book reviews]

Posted in Books, Kids, Mountains, pictures, Travel with tags , , , , , , , , , , , , , , , , , , , , on September 24, 2017 by xi'an

“‘Oh ye of little faith.’ Rebus picked up his lamb chop and bit into it.” Ian Rankin, Rather be the Devil

Rebus’ latest case, a stray cat, a tree that should not be there, psychological worries in Uppsala, maths formulas, these are the themes of some of my vacation books. I read more than usual because of the heavy rains we faced in Northern Italy (rather than Scotland!). Ian Rankin’s latest novel Rather be the Devil reunites most of the characters of past novels, from John Rebus to Siobhan Clarke, Malcolm Fox, Big Ger’ Cafferty, and others. The book is just as fun to read as the previous ones (but only if one has read those I presume!), not particularly innovative in its plot, which recalls some earlier ones, and a wee bit disappointing in the way Big Ger’ seems to get the upper hand against Rebus and the (actual) police. Nonetheless pleasant for the characters themselves, including the City of Edinburgh itself!, and the dialogues. Rebus is not dead yet (spoiler?!) so there should be more volumes to come as Rankin does not seem to manage without his trademark detective. (And the above quote comes in connection with the muttonesque puzzle I mention in my post about Skye.)

The second book is a short story by Takashi Hiraide called The Guest Cat (in French, The cat who came from Heaven, both differing from the Japanese Neko ko kyaku) and which reads more like a prose poem than like a novel. It is about a (Japanese) middle-aged childless couple living in a small rented house that is next to a beautiful and decaying Japanese garden. And starting a relation with the neighbours’ beautiful and mysterious cat. Until the cat dies, somewhat inexplicably, and the couple has to go over its sorrow, compounded by the need to leave the special place where they live. This does not sound much of a story but I appreciated the beautiful way it is written (and translated), as well as related to it because of the stray cat that also visits us on a regular basis! (I do not know how well the book has been translated from Japanese into English.)

The third book is called Debout les Morts (translated as The Three Evangelists) and is one of the first detective stories of Fred Vargas, written in 1995. It is funny with well-conceived characters (although they sometimes verge so much on the caricature as to make the novel neo-picaresque) and a fairly original scenario that has a Russian doll or onion structure, involving many (many) layers. I was definitely expecting anything but the shocking ending! The three main characters (hence the English translation title) in the novel are 35-ish jobless historians whose interests range from hunter-gatherers [shouldn’t then he be a pre-historian?!] to the Great [WWI] War, with a medieval expert in the middle. (The author herself is a medieval historian.) As written above, it is excessive in everything, from the characters to the plot, to the number of murders, but or maybe hence it is quite fun to read.

The fourth book is Kjell Eriksson‘s Jorden ma rämna that I would translate from the French version as The earth may well split (as it is not translated in English at this stage), the second volume of the Ann Lindell series, which takes place in Uppsala, and in the nearby Swede countryside. I quite enjoyed this book as the detective part was is almost irrelevant. To the point of having the killer known from the start. As in many Scandinavian noir novels, especially Swedish ones, the social and psychological aspects are predominant, from the multiple events leading a drug addict to commit a series of crimes, to the endless introspection of both the main character and her solitude-seeking boyfriend, from the failures of the social services to deal with the addict to a global yearning for the old and vanished countryside community spirit, to the replacement of genuine workers’ Unions by bureaucratic structures. Not the most comforting read for a dark and stormy night, but definitely a good and well-written book.

And the last book is yet again a Japanese novel by Yôko Ogawa, The Housekeeper and The Professor, which title in French is closer to the Japanese title, The professor’s favourite equation (博士の愛した数式), is about a invalid maths professor who has an 80 minutes memory span, following a car accident. His PhD thesis was about the Artin conjecture. And about his carer (rather than housekeeper) who looks after him and manages to communicate despite the 80 mn barrier. And about the carer’s son who is nicknamed Root for having a head like a square root symbol (!). The book is enjoyable enough to read, with a few basic explanations of number theory, but the whole construct is very contrived as why would the professor manage to solve mathematical puzzles and keep some memory of older baseball games despite the 80mn window. (I also found the naivety of the carer as represented throughout the book a wee bit on the heavy side.)

Not a bad summer for books, in the end!!!