Blog Archives

splitting a field by annealing

October 17, 2017
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splitting a field by annealing

A recent riddle [from The Riddle] that I pondered about during a [long!] drive to Luxembourg last weekend was about splitting a square field into three lots of identical surface for a minimal length of separating wire… While this led me to conclude that the best solution was a T like separation, I ran a […]

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Astrostatistics school

October 17, 2017
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Astrostatistics school

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 […]

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

October 9, 2017
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[summer Astrostat school] room with a view [jatp]

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 […]

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mea culpa!

October 8, 2017
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mea culpa!

An entry about our Bayesian Essentials book on X validated alerted me to a typo in the derivation of the Gaussian posterior..! When deriving the posterior (which was left as an exercise in the Bayesian Core), I just forgot the term expressing the divergence between the prior mean and the sample mean. Mea culpa!!!Filed under: […]

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Le Monde puzzle [#1021]

September 17, 2017
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Le Monde puzzle [#1021]

A puzzling Le Monde mathematical puzzle for which I could find no answer in the allotted time!: A most democratic electoral system allows every voter to have at least one representative by having each of the N voters picking exactly m candidates among the M running candidates and setting the size n of the representative […]

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Le Monde puzzle [#1020]

September 14, 2017
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Le Monde puzzle [#1020]

A collection of liars in this Le Monde mathematical puzzle: A circle of 16 liars and truth-tellers is such that everyone states that their immediate neighbours are both liars. How many liars can there be? A circle of 12 liars and truth-tellers is such that everyone state that their immediate neighbours are one liar plus […]

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Le Monde puzzle [#1018]

August 28, 2017
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Le Monde puzzle [#1018]

An arithmetic Le Monde mathematical puzzle (that first did not seem to involve R programming because of the large number of digits in the quantity involved): An integer x with less than 100 digits is such that adding the digit 1 on both sides of x produces the integer 99x.  What are the last nine […]

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sequence riddle

August 9, 2017
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sequence riddle

The riddle this week on The Riddler was about finding the largest sequence of integers between 1 and 100 such that each integer is only used once and always followed by a multiple or a factor. A basic R code searching at random [and programmed during a massive downpour on Skye] led to a solution […]

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Le Monde puzzle [#1707]

July 27, 2017
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Le Monde puzzle [#1707]

A geometric Le Monde mathematical puzzle: Given a pizza of diameter 20cm, what is the way to cut it by two perpendicular lines through a point distant 5cm from the centre towards maximising the surface of two opposite slices?  Using the same point as the tip of the four slices, what is the way to […]

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RNG impact on MCMC [or lack thereof]

July 12, 2017
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RNG impact on MCMC [or lack thereof]

Following the talk at MCM 2017 about the strange impact of the random generator on the outcome of an MCMC generator, I tried in Montréal airport the following code on the banana target of Haario et al. (1999), copied from Soetaert and Laine and using the MCMC function of the FME package: library(FME) Banana <- […]

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