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Introducing the Lowry Plot

January 11, 2011
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Introducing the Lowry Plot

Here at the Health and Safety Laboratory* we’re big fans of physiologically-based pharmacokinetic (PBPK) models (say that 10 times fast) for predicting concentrations of chemicals around your body based upon an exposure. These models take the form of a big system of ODEs. Because they contain many equations and consequently many parameters (masses of organs

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Le Monde puzzle [1]

January 10, 2011
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Le Monde puzzle [1]

Following the presentation of the first Le Monde puzzle of the year, I tried a simulated annealing solution on an early morning in my hotel room. Here is the R code, which is unfortunately too rudimentary and too slow to be able to tackle n=1000. #minimise \sum_{i=1}^I x_i #for 1\le x_i\le 2n+1, 1\e i\le I

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Abusing Amazon’s Elastic MapReduce Hadoop service… easily, from R

January 10, 2011
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Abusing Amazon’s Elastic MapReduce Hadoop service… easily, from R

JD Long's experimental segue package makes it easy to use Amazon's Elastic MapReduce service to fire up a Hadoop cluster and use it for non-Big Data, computationally-intensive tasks. The package provides a cluster-aware version of lapply() which "just works".

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Really useful bits of code that are missing from R

January 10, 2011
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Really useful bits of code that are missing from R

There are some pieces of code that are so simple and obvious that they really ought to be included in base R somewhere. Geometric mean and standard deviation – a staple for anyone who deals with lognormally distributed data. geomean <- function(x, na.rm = FALSE, trim = 0, ...) { exp(mean(log(x, ...), na.rm = na.rm,

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Building a fact-based world view

January 7, 2011
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Building a fact-based world view

Gapminder is an independent foundation based in Stockholm, Sweden. Its mission is “to debunk devastating myths about the world by offering free access to a fact-based world view“. They provide free online tools, data (more than 400 datasets freely available!) and videos “to better understand the changing world“. The initial development of Gapminder was the

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Arrogance sampling

January 7, 2011
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Arrogance sampling

A new posting on arXiv by Benedict Escoto on a simulation method for approximating normalising constants (i.e. evidence) with an eye-catching name! Here is the abstract This paper describes a method for estimating the marginal likelihood or Bayes factors of Bayesian models using non-parametric importance sampling (“arrogance sampling”). This method can also be used to

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a survey on ABC

January 6, 2011
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a survey on ABC

With Jean-Michel Marin, Pierre Pudlo and Robin Ryder, we just completed a survey on the ABC methodology. It is now both arXived and submitted to Statistics and Computing. Rather interestingly, our first draft was written in Jean-Michel’s office in Montpelier by collating the ‘Og posts surveying new ABC papers! (Interestingly because this means that my

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web content anlayzer

January 6, 2011
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web content anlayzer

Just developed a small crawler to check my online content at binfalse.de in terms of W3C validity and the availability of external links. Here is the code and some statistics...

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Graph gallery in R

January 6, 2011
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Graph gallery in R

R is sometime criticized for producing graphs not as elaborated as Matlab ones, or other softwares’. Here is a link to a graph gallery by Romain François to “enhance your data visualization with R”. The corresponding R code is given. Might be useful for ENSAE students for ‘statap’ projects. Below are four examples. The maps

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Short review of the R book

January 5, 2011
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Short review of the R book

David Scott wrote a review of Introducing Monte Carlo Methods with R in the International Statistical Review that is rather negative, since the main bulk reads as follows: I found some aspects of the book very disappointing. The first chapter (“Basic R Programming”) has some unfortunate mistakes and some statements, which are contentious at least

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