Archive for ABC in Helsinki

ABC in Helsinki [on-board]

Posted in pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , , , on May 17, 2016 by xi'an

abcruiseABC in Helsinki (a.k.a. ABCruise) has started! With a terrific weather most adequate for a cruise on the Baltic. The ship on which the workshop takes place is certainly larger than any I have been on, including the Channel ferries, and the inside alley looks rather like a shopping centre! However, the setting is exceptional, with comfy sea-facing cabins and pleasant breaks (including fancy tea!) Plus,  we have a quiet and cosy conference room that makes one forgets one is on a boat. Until it starts rocking. Or listing! The cruise boat is definitely large enough to be fairly stable. A unique experience we could consider for future (AB-see) workshops (with the caveat that we benefited from exceptional circumstances that brought the costs down to ridiculous amounts).

Richard Everitt talked about the synthetic likelihood approach and its connection with ABC. Making clear for me a point I had somewhat forgotten, namely that the approximative likelihood is a Gaussian at the observed summary statistics, but one centred at empirical moments derived from the simulation of pseudo summaries based on a given value of the parameter θ. So it is not an exact approach in that it does not converge to the true likelihood as the number of simulation grows to infinity. (While a kernel would converge.) That means it may (will) misrepresent the tails unless the distribution of the summary statistic is close to Normal. Richard also introduced bootstrap or bags of little bootstraps in order to speed up the generation of the pseudo-data, which makes sense albeit it moves the sampling away from the true model since it is conditional on  a single simulation.

Jean-Michel Marin introduced the ABC inference algorithm we are currently working on, using regression random forests that differ from the classification forests we used for model selection. (The paper is close to completion so I hope to be able to tell more in a near future!) Clara Grazian presented her semi-parametric work using ABC with Brunero Liseo. That was part of her thesis. Thomas Schön presented an extension of his particle Gibbs with adaptive sampling to the case of degenerate transitions, using an ABC approximation to get around this central problem. A very interesting entry that I need to study deeper. And Caroline Colijn talked about ABC for trees, mostly about the selection of summary statistics towards comparing tree topologies, with  a specific distance between trees that caters to the topology and only the topology.

ABC in Helsinki & Stockholm [deadline looming]

Posted in Kids, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , , on April 1, 2016 by xi'an

abcruiseIn case you have not yet registered for ABC in Helsinki (a.k.a. ABCruise), registration is open for just another week, with the all-inclusive fees of 200 euros for trip, cabin, talks, and meals! When registering you need to buy first a ticket on the Aalto University web shop: at some point, distinguishing between “Maksa” which means pay, and “Peruuta” which means cancel, may help! The submission of ABC posters is also encouraged till May 1, with emails to be sent to abcinhelsinki on gmail.

ABC in Helsinki & Stockholm [registration now open]

Posted in Kids, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , on February 22, 2016 by xi'an

abcruiseAs announced in earlier posts, ABC in Helsinki (a.k.a. ABCruise) will take place on May 16-18, 2016 on a regular cruise boat going from Helsinki, Finland,  on the 16th to Stockholm, Sweden, and back to Helsinki before noon on the 18th. The workshop takes place from noon on the 16th till noon on the 18th, with a short break around noon on the 17th in Stockholm. Registration is now open and the fees are an all-inclusive 200 euros for trip, cabin, and meals! Thanks to the organising committee for achieving such a bargain! Just do not wait for registering! The submission of posters is also encouraged, with emails to be sent to abcinhelsinki on gmail.

ABC in Helsinki, Stockholm, and in between [a.k.a., ABCruise]

Posted in Books, Kids, Statistics, Travel, University life with tags , , , , , , , , on October 28, 2015 by xi'an

As mentioned in a previous post, I had not pursued actively the organisation of an “ABC in…” workshop this year. I am thus very grateful to Jukka Corander, Samuel Kaski, Ritabrata Dutta, Michael Gutmann, from Helsinki, to have organised the next “ABC in…” workshop in Helsinki in the most possible exotic way, namely aboard a cruise ship going between Helsinki and Stockholm, on the Baltic Sea. Hence the appropriate ABCruise nickname. It will take place from May 16 to May 18, allowing for flying [from European cities] to Helsinki on the 16th and back from Helsinki on the 18th! While this may sound an inappropriate location for a meeting, we are constructing a complete scientific program with two days of talks [with a noon break in Stockholm], posters, and a total registration fee of 200€, including cabin and meals! (Which is clearly cheaper than having the same meeting on firm ground.) So, to all ‘Og’s readers interested in ABC topics, secure those dates in your agenda and keep posted for incoming updates on the program and the opening of registration.