Archive for August, 2010

New refereeing

Posted in Statistics, University life with tags , , on August 27, 2010 by xi'an

In a recent article, the New York Times describes the new approach to refereeing adopted by the Shakespeare Quarterly, namely to turn the refereeing process into a public on-line discussion.

“Mixing traditional and new methods, the journal posted online four essays not yet accepted for publication, and a core group of experts — what Ms. Rowe called “our crowd sourcing” — were invited to post their signed comments on the Web site MediaCommons, a scholarly digital network. Others could add their thoughts as well, after registering with their own names. In the end 41 people made more than 350 comments, many of which elicited responses from the authors. The revised essays were then reviewed by the quarterly’s editors, who made the final decision to include them in the printed journal.”

I find the move quite interesting, as well as worth repeating within our community. For one thing, nowadays, most papers are already available on arXiv. And sometimes the journal they are submitted to is also indicated on the abstract page. So introducing a (possibly monitored) forum of opinions about the paper [on arXiv or on the journal own webpage] would not be a major difficulty. And could come as a complement to the usual refereeing process. As posted in an earlier post (?), I actually am in favour of removing anonymity for the usual referees as well, possibly on a voluntary basis, as I do not see a huge risk of a bias coming from this move, while it should speed up the refereeing process. The double-blind policy adopted by JASA and JCGS, among others, does not strike me as efficient.

Sunrise on Long Beach

Posted in pictures, Travel with tags , , on August 27, 2010 by xi'an

Impressions on Yosemite

Posted in Kids, Mountains, Travel with tags , , , on August 26, 2010 by xi'an

After reading and re-reading Lynn Hill’s Climbing Free: My Life in the Vertical World. and of her ascents in the Yosemite valley, I was definitely looking forward my visit there… While not planning to do any climbing there, I was expecting some out-worldy quality from the place. The first vision of the valley when getting out of the Route 41 tunnel is indeed stunning with the perfect face of El Capitan blocking most of the view. The thousand vertical meters of the face are both daunting and oppressive!

Nonetheless, my overall impression of Yosemite is more one of a gigantic parking lot with nice walls than of a Mecca of big wall climbing… The place is simply bursting at the seams due to the inappropriate number of visitors there and to the complete lack of size control. Cars are parked everywhere, traffic jams block the approaching roads for miles and there are people everywhere one goes… If there is a place where limiting the number of visitors & cars per day would make sense, it is Yosemite. (There are only two access roads and both only lead to the Yosemite valley, so having the Park counting the ins and outs is feasible.) A numerus clausus on the visitors would recover the majesty of the place which has clearly vanished under the cars, garbage bins and flows of shoppers. (By comparison, Banff is also highly popular but the crowd concentrates inside the village, which can be avoided rather easily.) Both hikes I did in the valley were classified as strenuous and very strenuous, respectively, but there were still crowds on both paths, with equipments ranging from the backcountry heavy bagpacks to the flip-flops plus bathing suits. The paths themselves were paved or even tarred, most likely because of the intense traffic they were submitted to. (Even the fairly steep path to the Upper Yosemite Falls that I rounded in a bit more than two hours has its share of unconscious tourists with improper shoes and no water and its paved sections…)

Even the upper range of Glacier Point was victim of the same plague, despite its distance from the centre. Rows of cars, jams at the parking lot at sunset and sunrise, ill-equipped hikers climbing to the top of Sentinel Dome. Except for a deer foraging for food in the valley main parking lot and rodents begging for scraps from hikers, I did not see any sign of wildlife during my week there. Nor did I come across any climber. My most enjoyable moment of the trip was one hour of bouldering in the forest near Yosemite West, where we stayed. By myself.) Terrible impressions, thus, of a Disney-esque caricature of a national park…

Read Paper 13/10/10

Posted in Statistics, University life with tags , , , , on August 25, 2010 by xi'an

There will be an RSS Read Paper session on October 13 given by Marc Girolami and B. Calderhead on Riemann manifold Langevin and Hamiltonian Monte Carlo methods that I definitely plan to attend. Here is the abstract:

The paper proposes Metropolis adjusted Langevin and Hamiltonian Monte Carlo sampling methods defined on the Riemann manifold to resolve the shortcomings of existing Monte Carlo algorithms when sampling from target densities that may be high dimensional and exhibit strong correlations. The methods provide fully automated adaptation mechanisms that circumvent the costly pilot runs that are required to tune proposal densities for Metropolis-Hastings or indeed Hamiltonian Monte Carlo and Metropolis adjusted Langevin algorithms. This allows for highly efficient sampling even in very high dimensions where different scalings may be required for the transient and stationary phases of the Markov chain. The methodology proposed exploits the Riemann geometry of the parameter space of statistical models and thus automatically adapts to the local structure when simulating paths across this manifold, providing highly efficient convergence and exploration of the target density. The performance of these Riemann manifold Monte Carlo methods is rigorously assessed by performing inference on logistic regression models, log-Gaussian Cox point processes, stochastic volatility models and Bayesian estimation of dynamic systems described by non-linear differential equations. Substantial improvements in the time-normalized effective sample size are reported when compared with alternative sampling approaches. MATLAB code that is available from the authors allows replication of all the results reported.

and as usual (400 word) comments can be submitted without any restriction.

Art brut

Posted in Kids, pictures, Travel with tags , , on August 25, 2010 by xi'an


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