2040 search results for "twitter"

Initial Work on a Post Not Yet Completed

January 12, 2011
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Initial Work on a Post Not Yet Completed

It’s no secret I have been learning R for some time now, and one of the best resources out there is the hashtag rstats on twitter (#rstats).  There is a tremendous community of active users who are always willing to help, but not to mention, you can get a first hand view of some of

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Random variable generation (Pt 3 of 3)

January 12, 2011
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Random variable generation (Pt 3 of 3)

Ratio-of-uniforms This post is based on chapter 1.4.3 of Advanced Markov Chain Monte Carlo.  Previous posts on this book can be found via the  AMCMC tag. The ratio-of-uniforms was initially developed by Kinderman and Monahan (1977) and can be used for generating random numbers from many standard distributions. Essentially we transform the random variable of

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Two short Bayesian courses in South’pton

January 12, 2011
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Two short Bayesian courses in South’pton

An announcement for two short-courses on Introduction to  Bayesian Analysis and MCMC, and Hierarchical Modelling of Spatial and Temporal Data by Alan Gelfand (Duke University, USA) and Sujit Sahu (University of Southampton, UK), are to take place in Southampton on June 7-10, this year. Course 1: Introduction to Bayesian Analysis and MCMC. Date: June 7,

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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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