R-bloggers announcement – maintenance mode – site might be down

posted on ·  
retrieved on September 2, 2010 ·  
Hello dear followers of R-bloggers.com Today (and probably in the next few days), R-bloggers will be down part of the time due to maintenance work. (Technical stuff: I am moving the site from shared hosting to VPS, and there seem to be a few bumps in the road) Sorry for the inconvenience, I will update once it would look like we are in the clear. Best, Tal Galili
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Bot Botany – K-Means and ggplot2

posted on R-Chart ·  
retrieved on September 2, 2010 ·  
Bot Botany – K-Means and ggplot2
So if you had a robot that was an expert at botany - would you have a bot botanist?  Among other things, it would need to to distinguish flowers through vision and image processing, and be able to classify various kinds of plants based upon specific characteristics.  What do both of these requirements have in common?   They can be done using the k-means clustering.  Image segmentation can be used to allow our robot to recognize objects.  Based upon petal and sepal size, it could determine say - the species of ...
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New R User Group in New Jersey

posted on Revolutions ·  
retrieved on September 2, 2010 ·  
Folks in the New Jersey area no longer need to trek over to New York City to meet other R users. Now there's NewJerseyR, a new R user group put together by Mango Solutions. The first meeting will in Iselin on September 16, with speakers from Mango, Pfizer, and Bristol Myers Squibb. Full details at the NewJerseyR website, linked below.NewJerseyR: NewJerseyR home page (Follow the link for other posts by David Smith)
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Statisfaction

posted on Xi'an's Og » R ·  
retrieved on September 2, 2010 ·  
Statisfaction
A collective blog has been started by the statistics students and postdocs at CREST, in the wake of the Valencia meeting. It is called Statisfaction. (The Rolling Stones of Statistics?! Actually, Andrew Gelman also has a post with that title… And it is even part of the Urban Dictionnary!) Since I have no responsability nor even say in the contents of this independent blog, I cannot help but recommend following it! The latest posting is about the slides of Peter Müller’s slides of his Santa Cruz course in Bayesian nonparametrics ...
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How the expiration of the assault weapon ban affected Mexico

posted on Diego Valle's Blog ·  
retrieved on September 2, 2010 ·  
How the expiration of the assault weapon ban affected Mexico
There has been a lot of attention paid to the role of US guns exacerbating the violence in Mexico. The assault-weapon ban expired on September 14, 2004, but with the recent spiraling of violence in Mexico the ban has attracted renewed attention. Just recently the Mexican President stood before the American Congress and blamed the assault weapon ban for the rising violence in Mexico, seemingly without proof. This post will try to clarify some of the issues surrounding the controversy. I think it would be fair to say that ...
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Third, and Hopefully Final, Post on Correlated Random Normal Generation (Cholesky Edition)

posted on Cerebral Mastication » R ·  
retrieved on September 2, 2010 ·  
Third, and Hopefully Final, Post on Correlated Random Normal Generation (Cholesky Edition)
André-Louis Cholesky is my homeboy When I did a brief post three days ago I had no plans on writing two more posts on correlated random number generation. But I’ve gotten a couple of emails, a few comments, and some Twitter feedback. In response to my first post, Gappy, calls me out and says, “the way mensches do multivariate (log)normal variates is via Cholesky. It’s simple, instructive, and fast.”  And I think we’re all smart enough to read through Mr. Gappy’s comment and see that he’s saying I’m a complicated, opaque, ...
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Stochastic approximation in Bristol

posted on Xi'an's Og » R ·  
retrieved on September 2, 2010 ·  
Stochastic approximation in Bristol
This is very short notice, but for those in the vicinity and not at the RSS conference, there is a highly interesting workshop taking place in Bristol in ten days (I would certainly have gone, had I not been at the same time in Banff!): We would like to invite you to contribute to our 3 day workshop on “Stochastic approximation: methodology, theory and applications in statistics” that will take place in the Mathematics Department of the University of Bristol (UK) from 13-15 September 2010. The aim of this workshop is ...
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Rllvm

posted on Omegahat Statistical Computing » R ·  
retrieved on September 1, 2010 ·  
Rllvm
Over the past 10 years, I have been torn between building a new stat. computing environment or trying to overhaul R. There are many issues on both sides. But the key thing is to enable doing new and better things in stat. computing rather than just making the existing things easier and more user-friendly. If we are to continue with R for the next few years, it is essential that it get faster. There are many aspects to this. One is compiling interpreted R code into something faster. LLVM is a toolkit that facilitates ...
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Rffi

posted on Omegahat Statistical Computing » R ·  
retrieved on September 1, 2010 ·  
Rffi
A few weeks ago, I posted the Rffi package on the Omegahat repository. It is an interface to libffi which is a portable mechanism for invoking native routines without having to write and compile any wrapper routines in the native language. In other words, we can use this in R to call C routines using only R code. This enables us to call arbitrary routines and get back arbitrary values, including structures arrays, unions, etc. One could use the RGCCTranslationUnit package to obtain descriptions of routines and data structures and then generate the interfaces to those routines ...
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How to generate correlated random numbers

posted on Revolutions ·  
retrieved on September 1, 2010 ·  
We've covered how to generate random numbers in R before, but what if you want to go beyond generating one random number at a time? What if you want to generate two, or three or more random numbers, and what's more, you want them to be correlated?JD Long lays out the way in a couple of posts at his Cerebral Mastication blog. If you want to generate bivariate (or trivariate, or more) random multivariate Normal variates, it's pretty easy, as JD points out. Just use the mvrnorm function from the ...
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