Archive for Ottawa

O’Bayes 19/2

Posted in Books, pictures, Running, Travel, University life with tags , , , , , , , , , , , , , , , , , on July 1, 2019 by xi'an

One talk on Day 2 of O’Bayes 2019 was by Ryan Martin on data dependent priors (or “priors”). Which I have already discussed in this blog. Including the notion of a Gibbs posterior about quantities that “are not always defined through a model” [which is debatable if one sees it like part of a semi-parametric model]. Gibbs posterior that is built through a pseudo-likelihood constructed from the empirical risk, which reminds me of Bissiri, Holmes and Walker. Although requiring a prior on this quantity that is  not part of a model. And is not necessarily a true posterior and not necessarily with the same concentration rate as a true posterior. Constructing a data-dependent distribution on the parameter does not necessarily mean an interesting inference and to keep up with the theme of the conference has no automated claim to [more] “objectivity”.

And after calling a prior both Beauty and The Beast!, Erlis Ruli argued about a “bias-reduction” prior where the prior is solution to a differential equation related with some cumulants, connected with an earlier work of David Firth (Warwick).  An interesting conundrum is how to create an MCMC algorithm when the prior is that intractable, with a possible help from PDMP techniques like the Zig-Zag sampler.

While Peter Orbanz’ talk was centred on a central limit theorem under group invariance, further penalised by being the last of the (sun) day, Peter did a magnificent job of presenting the result and motivating each term. It reminded me of the work Jim Bondar was doing in Ottawa in the 1980’s on Haar measures for Bayesian inference. Including the notion of amenability [a term due to von Neumann] I had not met since then. (Neither have I met Jim since the last summer I spent in Carleton.) The CLT and associated LLN are remarkable in that the average is not over observations but over shifts of the same observation under elements of a sub-group of transformations. I wondered as well at the potential connection with the Read Paper of Kong et al. in 2003 on the use of group averaging for Monte Carlo integration [connection apart from the fact that both discussants, Michael Evans and myself, are present at this conference].

stop the rot!

Posted in Statistics with tags , , , , , , , , , , , , on September 26, 2017 by xi'an

Several entries in Nature this week about predatory journals. Both from Ottawa Hospital Research Institute. One emanates from the publication officer at the Institute, whose role is “dedicated to educating researchers and guiding them in their journal submission”. And telling the tale of a senior scientist finding out a paper submitted to a predatory journal and later rescinded was nonetheless published by the said journal. Which reminded me of a similar misadventure that occurred to me a few years ago. After having a discussion of an earlier paper therein rejected from The American Statistician, my PhD student Kaniav Kamary and I resubmitted it to the Journal of Applied & Computational Mathematics, from which I had received an email a few weeks earlier asking me in flowery terms for a paper. When the paper got accepted as such two days after submission, I got alarmed and realised this was a predatory journal, which title played with the quasi homonymous Journal of Computational and Applied Mathematics (Elsevier) and International Journal of Applied and Computational Mathematics (Springer). Just like the authors in the above story, we wrote back to the editors, telling them we were rescinding our submission, but never got back any reply or request of copyright transfer. Instead, requests for (diminishing) payments were regularly sent to us, for almost a year, until they ceased. In the meanwhile, the paper had been posted on the “journal” website and no further email of ours, including some from our University legal officer, induced a reply or action from the journal…

The second article in Nature is from a group of epidemiologists at the same institute, producing statistics about biomedical publications in predatory journals (characterised as such by the defunct Beall blacklist). And being much more vehement about the danger represented by these journals, which “articles we examined were atrocious in terms of reporting”, and authors submitting to them, as unethical for wasting human and animal observations. The authors of this article identify thirteen characteristics for spotting predatory journals, the first one being “low article-processing fees”, our own misadventure being the opposite. And they ask for higher control and auditing from the funding institutions over their researchers… Besides adding an extra-layer to the bureaucracy, I fear this is rather naïve, as if the boundary between predatory and non-predatory journals was crystal clear, rather than a murky continuum. And putting the blame solely on the researchers rather than sharing it with institutions always eager to push their bibliometrics towards more automation of the assessment of their researchers.

O Canada! [Happy 150th birthday!]

Posted in Statistics with tags , , , , , , , , on July 1, 2017 by xi'an

I am just taking off from Paris to Montréal today for MCM 2017, on Canada Day which happens to be the 150th National Day. I have already spent three instances of a Canada Day, in both Ottawa and Banff, but this is the first in Québec and I am curious to see the atmosphere in Montréal for this occasion. If there is anything to see, since the Montréal Jazz Festival is already started…

20,000 pink ladies [10k: 37’26”, 43rd & 3rd V2]

Posted in Kids, Mountains, pictures, Running, Travel with tags , , , , , , , , on June 22, 2014 by xi'an

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This year was a special year for the races of Les Courants de la Liberté, in Caen, as part of the celebrations of the 70th anniversary of the Allied landing on the nearby D-Day beaches. The number of women running the Rochambelle race/walk against breast cancer was raised this year to 20,000 participants, an impressive pink wave riding the streets of Caen, incl. my wife, mother and mother-in-law! And even one of the 1944 Rochambelle nurses attending the start and finish of the race!

While I had no particular expectation for the 10k race, it went on so well that I ended up with my best time ever on this distance (my previous record was in Ottawa in July…1989!). The weather was perfect, cool and cloudy with a tailwind most of the way. (The low intensity training in Edinburgh and the Highlands may have helped.) I had a bit of an issue at the beginning passing the first rows of runners who were clearly in the wrong league but stuck with a runner most of the race, which helped with the middle hardest k’s (with a maximal 3:58 on the 8th k!), and  finished by motivating another V2 to keep up with, very glad to see my finish time. I actually ended up 3rd V2 just ahead of two other runners from this category, but there is no podium or reward for this in this race, given the large number of races to accommodate (ultra-trail of D-Day beaches, marathon, half-marathon, 10k, rollers, kids,…)

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