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On Dirichlet’s approximation theorem

June 19, 2011
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On Dirichlet’s approximation theorem

This is one of my favourites: in 1840 the German mathematician Dirichlet proved an elegant theorem, known as “Dirichlet’s approximation theorem“. The proof is surprisingly simple, but the usefulness of the proposition in some fields of mathematics, such as Diophantine analysis is remarkable. It goes as follows: Let a be a real number and N

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R-bloggers

June 19, 2011
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R-bloggers

This humble blog is proudly part of R-bloggers, since a couple of weeks. I had this website as my homepage for some months now and I have found therein really inspiring and informative things. So I wish all the best to Tal Galili and his great job with...

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Tracking execution paths

June 18, 2011
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Tracking execution paths

Earlier this week, I was trying to figure out the path of execution through a big chunk of code. Once you reach a certain size of codebase, tracking which function gets called when can be tricky. My first thought for dealing with this was to add a message line at the start of each function

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Raster, CMSAF and solaR

Raster, CMSAF and solaR

The Satellite Application Facility on Climate Monitoring (CMSAF) generates, archives and distributes widely recognised high-quality satellite-derived products and services relevant for climate monitoring in operational mode. The data is freely accesible here after a registration process. I have ask them for several files with monthly averages of global solar radiation over the Iberian Peninsula (download).

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solaR 0.24 at CRAN

solaR 0.24 at CRAN

The version 0.24 of solaR is at CRAN and R-Forge. Some days before the 0.23 version was uploaded, but I had to make a quick fix to readMAPA: the url of http://www.mapa.es/siar has been changed to http://www.marm.es/siar. Moreover, this function has been renamed to readSIAR, although it is still available as readMAPA. Consequently the mode

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5000 R questions on stackoverflow.com

June 16, 2011
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The R tag on stackoverflow.com hit a milestone yesterday: 5000 questions about the R language. (The 5000th question was about the fortunes package, incidentally -- thanks to Andrie de Vries for pointing this out on Twitter.) Stackoverflow.com continue...

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Character occurrence in passwords

June 16, 2011
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Character occurrence in passwords

As everyone knows, it seems that Sony is taking a bit of a battering from hackers.  Thanks to Sony, numerous account and password details are now circulating on the internet. Recently, Troy Hunt carried out a brief analysis of the password structure. Here is a summary of his post: There were around 40,000 passwords, of which

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Further Bernoulli factories

June 15, 2011
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Further Bernoulli factories

Yesterday, Andrew Thomas and José Blanchet posted a note on the Bernouilli factory on arXiv. This short paper links with the recent paper of Flegal and Herbei I commented earlier. Considering the special target Thomas and Blanchet develop an elaborate scheme of cascading envelopes that converge to f from above. Their paper is very clear

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Embedding a time series with time delay in R — Part II

June 14, 2011
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Embedding a time series with time delay in R — Part II

Some months ago, I posted a function that extended the base R function embed() to allow for time delay embedding. Today, David Gonzales alerted me to an inconsistency between embed() and Embed(). The example David used was where Embed() clearly … Continue reading →

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Wilcoxon Champagne test

June 14, 2011
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Wilcoxon Champagne test

As an appetizer for Paris triathlon, Jérôme and I ran as a team last week-end an adventure racing in Champagne region (it mainly consists in running, cycling, canoeing, with a flavor of orienteering, and Champagne is kept for the end). It was organized by Ecole Polytechnique students who, for the first time, divided Saturday’s legs

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