Nonconvexity, and playing indoor paintball

April 6, 2012
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Nonconvexity, and playing indoor paintball

Following the two previous posts (here and there), on the number of people that don't get wet while playing with water pistols, consider now an indoor version, in a non-convex room (i.e. player behind wall are now, somehow, protected). In the previ...

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Dynamite plots in R

April 6, 2012
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Dynamite plots in R

For some time I've contemplated creating a function for creating the dynamite plots beloved by many of the applied sciences. There's a lot of criticism regarding their utility, and there are several ways that present data in a more intelligible way. A search on the subject brings up pages with such emotive titles as "Dynamite plots: unmitigated evil?"...

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The 50 most used R packages

April 5, 2012
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The 50 most used R packages

Ask anyone what makes R a great language, one argument that often comes back is its very active community. Proof is the impressive number of packages contributed by developers from all horizons and backgrounds. The CRAN website alone lists 3,725 p...

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Compete in the Data Science Hackathon, April 28

April 5, 2012
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All around the world at noon GMT on April 28, data scientists around the world will compete in the world's first one-day International Data Science Hackathon, organized by Data Science London. Participants will receive a data set at the beginning of the event, and work in teams of 3-5 over the following 24 hours to create the best predictive...

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An intro to R

April 5, 2012
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An intro to R

A few weeks back I gave a talk at the local Berkeley R meetup group. The idea was to help people not make the same mistakes I made when I first started out learning R. It was the first time I made an entire presentation with Deck.js and I generated the syntax highlighted R code

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Use file.choose to customize output filenames in R functions

April 5, 2012
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In this post, I want to address the following issue: several data files with a common trame have to be dealt with by an R function. The function should export files (such as images or data files or any other file type). I explain how to create filenames such that the function automatically exports files in the same directory...

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useR! 2012 Deadlines Approaching: Registration, Hotels, Student Scholarships

April 5, 2012
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useR! 2012 Deadlines Approaching: Registration, Hotels,  Student Scholarships

Forwarded from Frank Harrell: DEADLINES FAST APPROACHING – 8th Annual International R User Conference useR! 2012, Nashville, Tennessee USA Registration Deadlines: Early Registration: Passed Regular Registration: Mar 1- May 12 Late Registration: May 13 – June 4 On-Site Registration: June 12 – June 15 Please note: Nashville is offering several large entertainment events the month

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Gaussian process regression with R

April 5, 2012
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Gaussian process regression with R

I’m currently working my way through Rasmussen and Williams’s book on Gaussian processes. It’s another one of those topics that seems to crop up a lot these days, particularly around control strategies for energy systems, and thought I should be able to at...

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Basics of Working With Data in R

April 5, 2012
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(This article was first published on R Video Tutorials - Stats Make Me Cry, and kindly contributed to R-bloggers) To leave a comment for the author, please follow the link and comment on his blog: R Video Tutorials - Stats Make Me Cry. R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: visualization (ggplot2,...

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Basics of Working With Data in R

April 5, 2012
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Where hiding if you don’t want to get wet ?

April 5, 2012
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Where hiding if you don’t want to get wet ?

Following the previous post, two additional remarks. Following a comment by @cosi, I have investigated quickly a binomial fit to the distribution of the number of people not getting wet, with a fixed number of players on the field. It looks like it...

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Melt

April 5, 2012
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There are many situations where data is presented in a format that is not ready to dive straight to exploratory data analysis or to use a desired statistical method. The reshape2 package for R provides useful functionality to avoid having to hack data around in a spreadsheet prior to import into R. The melt function

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A Little Web Scraping Exercise with XML-Package

April 5, 2012
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Some months ago I posted an example of how to get the links of the contributing blogs on the R-Blogger site. I used readLines() and did some string processing using regular expressions.With package XML this can be drastically shortened - see this:# get...

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R Structure Explained

April 4, 2012
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This post by Suraj Gupta explains it all. This is the first time I have seen a  concise and accessible explanation of the R environment structure and why it matters.   Addendum: This one by Digithead is also pretty good

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R Structure Explained

April 4, 2012
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This post by Suraj Gupta explains it all. This is the firs time I have seen a  concise and accessible explanation of the R environment structure and why it matters.   Addendum: This one by Digithead is also pretty good

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R, I Love You

April 4, 2012
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It is easier to critique than it is to create. I write this post with much gratitude for R, the R community and particularly R-Core who are paid $0 to bring us R. I’d like to offer an idea and I’m wondering if people are interested in ral...

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Data Science Undefined

April 4, 2012
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One of the favorite bar room discussions of statisticians, machine learners, and computer scientists is – what is data science? (And I don’t care whether it happens in a bar or not, it’s a “bar room” discussion by virtue of...

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How I Learned to Stop Worrying and Love Twitter

April 4, 2012
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In honor of Twitter making the decision to come to Detroit, here’s a special post on how I became a Twitter user. … At 3:30pm my wife called me. There was a shooting where my brother-in-law works at UPMC Western...

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How R finds objects (or, what that :: operator is for)

April 4, 2012
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How R finds objects (or, what that :: operator is for)

Most of the time when we're programming in R, we don't think about how R gets from an object name (say, "stdev") to what it represents (a function to calculate standard deviation, perhaps). If you're writing functions, you've probably know about R's lexical scoping. And if you use a lot of packages, you probably know about the search list,...

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Simulated Annealing in Julia

April 4, 2012
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Simulated Annealing in Julia

Building Optimization Functions for Julia In hopes of adding enough statistical functionality to Julia to make it usable for my day-to-day modeling projects, I’ve written a very basic implementation of the simulated annealing (SA) algorithm, which I’ve placed in the same JuliaVsR GitHub repository that I used for the code for my previous post about

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Enjoy Low Income Tax Rates

April 4, 2012
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Enjoy Low Income Tax Rates

Tax rates were higher in the past... Joe derisively snorted at the pay stub in his hand. Crumpling it into a ball, he wound up like a baseball pitcher and fast-balled the wad of paper across the room. It bounced unsatisfyi...

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New Release of ROracle posted to CRAN

April 4, 2012
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Oracle recently updated ROracle to version 1.1-2 on CRAN with enhancements and bug fixes. The major enhancements include the introduction of support for Oracle Wallet Manager and datetime and interval types.  Oracle Wallet ...

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Resampling Hierarchically Structured Data Recursively

April 4, 2012
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Resampling Hierarchically Structured Data Recursively

That's a mouthful! I presented this topic to a group of Vandy statisticians a few days ago. My notes (essentially reproduced in this post) are recorded at the Dept. of Biostatistics wiki: HowToBootstrapCorrelatedData. The presentation covers some bootstrap strategies for hierarchically structured (correlated) data, but focuses on the multi-stage bootstrap; an extension of that described

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Obama administration unveiled a Big Data Research and Development Initiative with $200 million

April 4, 2012
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Obama administration unveiled a Big Data Research and Development Initiative with $200 million

Yanchang Zhao, RDataMining.com Obama administration unveiled a Big Data Research and Development Initiative with $200 million on March 29, 2012, to improve the ability to extract knowledge and insights from large and complex collections of digital data. Six Federal departments … Continue reading →

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Betas of the low vol cohorts

April 4, 2012
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Betas of the low vol cohorts

How did the constraints affect portfolio betas, and how did the betas change over time? Previously “Low (and high) volatility strategy effects” created 6 sets of random portfolios — the so-called low vol cohorts — as of 2007 and showed their performance up to about a month ago. “Rebalancing the low vol cohorts” looked at … Continue reading...

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How R Searches and Finds Stuff

April 4, 2012
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How R Searches and Finds Stuff

Or… How to push oneself down the rabbit hole of environments, namespaces, exports, imports, frames, enclosures, parents, and function evaluation? Motivation There are a few reasons to bother reading this post: Rabbit hole avoida...

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Rudd, the last one standing?: Federal implications of QLD state election results

April 4, 2012
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Rudd, the last one standing?: Federal implications of QLD state election results

Labor won 15 of Queensland’s 29 House of Reps seats in the 2007 Federal election (AEC details here). Yet just three years later, in the 2010 Federal election, Labor won only 8 of 30 Queensland Reps seats, with 33.6% of 1st preferences (a swing of -9.3 percentage points). Labor’s best performance on 1st preferences in

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Review: Kölner R Meeting 30 March 2012

April 4, 2012
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Review: Kölner R Meeting 30 March 2012

The first Kölner R user meeting was great fun. About 20 useRs had turned up to exchange their ideas, questions and experience with R. Three talks about R & Excel, ggplot2 & XeLaTeX and Dynamical systems with R & simecol had kicked off the evening, wit...

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Regression – covariate adjustment

April 3, 2012
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Linear regression is one of the key concepts in statistics . However, people are often confuse the meaning of parameters of linear regression - the intercept tells us the average value of y at x=0, while the slope tells us how m...

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