Archive for London

simulating the pandemic

Posted in Books, Statistics with tags , , , , , , , , , , , on November 28, 2020 by xi'an

Nature of 13 November has a general public article on simulating the COVID pandemic as benefiting from the experience gained by climate-modelling methodology.

“…researchers didn’t appreciate how sensitive CovidSim was to small changes in its inputs, their results overestimated the extent to which a lockdown was likely to reduce deaths…”

The argument is essentially Bayesian, namely rather than using a best guess of the parameters of the model, esp. given the state of the available data (and the worse for March). When I read

“…epidemiologists should stress-test their simulations by running ‘ensemble’ models, in which thousands of versions of the model are run with a range of assumptions and inputs, to provide a spread of scenarios with different probabilities…”

it sounds completely Bayesian. Even though there is no discussion of the prior modelling or of the degree of wrongness of the epidemic model itself. The researchers at UCL who conducted the multiple simulations and the assessment of sensitivity to the 940 various parameters found that 19 of them had a strong impact, mostly

“…the length of the latent period during which an infected person has no symptoms and can’t pass the virus on; the effectiveness of social distancing; and how long after getting infected a person goes into isolation…”

but this outcome is predictable (and interesting). Mentions of Bayesian methods appear at the end of the paper:

“…the uncertainty in CovidSim inputs [uses] Bayesian statistical tools — already common in some epidemiological models of illnesses such as the livestock disease foot-and-mouth.”

and

“Bayesian tools are an improvement, says Tim Palmer, a climate physicist at the University of Oxford, who pioneered the use of ensemble modelling in weather forecasting.”

along with ensemble modelling, which sounds a synonym for Bayesian model averaging… (The April issue on the topic had also Bayesian aspects that were explicitely mentionned.)

false value

Posted in Statistics with tags , , , , , , , , , , , on November 23, 2020 by xi'an

A very pleasant eighth volume in the Rivers of London series after a few so-so episodes! The relentless deadpan of Peter Grant is back full shape, the plot is substantial and gripping, new and well-drawn characters abound, and the story offers an original retelling of the Difference Engine. (Not that I have reservations about Gibbson’s plus Sterling’s 1990 version!) Including mentions of Jacquard’s loom, card fed organ automates, Ada Lovelace and Mary Somerville. Plus providing great satire on Ai companies with a hardly modified “Deep Thought” pastiche. Enjoyable all along and definitely a page turner that I read within three days..! And being strongly immersed in the current era, from the passing away of David Bowie to the dearful impact of Theresa May as home secretary. Presumably missing a heap of references to geek culture and subcultures, apart from Hitchhiker Guide to the Galaxy. And too many quotes to report, but some mentions of stats (“the Red Army had done a statistical analysis with demon traps just as they had with conventional minefields. The conclusions had been the same in both cases.” (p.50) and “Beverley climbed into the bath with a second-hand copy of Statistics for Environmental Science and Management” (p.69), which is a genuine book.) As often the end is a bit murky and a bit precipitated, but not enough to whine about. Recommended (conditional on having read the earliest ones in the series)!

Haldane’s short autobiography

Posted in Books, pictures, Statistics with tags , , , , , , , , , , , , , , , , , , , , , , , , on October 15, 2020 by xi'an

“I was born at Oxford, England, in 1892.  My father was Prof. J.S. Haldane, the physiologist.  I was educated at Eton and New College, Oxford.  I learned much of my science by apprenticeship, assisting my father from the age of eight onwards, and my university degree is in for classics, not science.  I was in a British infantry battalion from 1914 to 1919, and was twice wounded.  I began scientific research in 1910, and became a Fellow of New College, Oxford, in 1919.  I was at Cambridge from 1922-1932 as Reader in Biochemistry, and have been a professor in London University since 1933.  I was visiting professor in the University of Berkeley, Cal., in 1932.  In the same year I was elected a Fellow of the Royal Society of London.

My scientific work has been varied.  In the field of human physiology I am best known for my work on the effects of taking large amounts of ammonium chloride and other salts.  This has had some application in treating lead and radium poisoning.  In the field of genetics I was the first to discover linkage in mammals, to map a human chromosome, and (with Penrose) to measure the mutation rate of a human gene.  I have also made some minor discoveries in mathematics.

Whilst I may have been a credit to my universities, I have been a trial in other ways.  I was dismissed from Cambridge University in 1926 in connexion with a divorce case, but regained my post on appeal to a higher tribunal, which found that the university authorities had decided to dismiss me without hearing my case.  At present I have refused to evacuate University College, London, and, with two assistants am its sole academic occupant.  I am carrying on research there under difficulties.

Besides strictly scientific books I have written a number of popular works including a book of children’s stories.  I consider that a scientist, if he can do so, should help to render science intelligible to ordinary people, and have done my best to popularize it.

Till 1933 I tried to keep out of politics, but the support given by the British Government to Hitler and Mussolini forced me to enter the political field.  In 1936-1938 I spent three months in Republican Spain, first as an adviser on gas protection, and then as an observer of air raid precautions.  I was in the front line during fighting, and in several air raids behind the line.  Since then I have tried, with complete lack of success, to induce the British Government to adopt air raid protection measures which had proved their efficacy in Spain.

Mr. Chamberlain’s policy, and the recent developments in physics and biology, combined to convince me of the truth of the Marxist philosophy.  Though I am a member of no political party, I have of late years supported the communist party on a number of issues.  At present I am engaged on research in genetics, & research intended to save the lives of members of the British armed forces, and writing and public speaking designed to prevent the spreading of the present war, and if possible to bring about peace.  I am a fairly competent public speaker.

It will be seen that my life has been a full one.  I have been married for 14 years, measure 73 inches, weigh 245 pounds, and enjoy swimming and mountain walking.  I am bald and blue-eyed, a moderate drinker and a heavy smoker. I can read 11 languages and make public speeches in three, but am unmusical.”

J.B.S. Haldane, circa 1940

postdoc at Warwick on robust SMC [call]

Posted in Kids, pictures, R, Statistics, University life with tags , , , , , , , , on January 11, 2020 by xi'an

Here is a call for a research fellow at the University of Warwick to work with Adam Johansen and Théo Damoulas on the EPSRC and Lloyds Register Foundaton funded project “Robust Scalable Sequential Monte Carlo with application to Urban Air Quality”. To quote

The position will be based primarily at the Department of Statistics of the University of Warwick. The post holder will work closely in collaboration with the rest of the project team and another postdoctoral researcher to be recruited shortly to work within the Data Centric Engineering programme at the Alan Turing Institute in London. The post holder will be expected to visit the Alan Turing Institute regularly.

Candidates with strong backgrounds in the mathematical analysis of stochastic algorithms or sequential Monte Carlo methods are particularly encouraged to apply. Closing date is 19 Jan 2020.

Art Ensemble of Chicago

Posted in Kids, pictures, Travel with tags , , , , , , , , , on December 21, 2019 by xi'an