Blog Archives

Seeing the Big Picture

September 23, 2010
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Here’s a nice snippet from a 2009 article by Kass that I read yesterday: According to my understanding, laid out above, statistical pragmatism has two main features: it is eclectic and it emphasizes the assumptions that connect statistical models with observed data. The pragmatic view acknowledges that both sides of the frequentist-Bayesian debate made important

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Why Use ProjectTemplate or Any Other Framework?

September 19, 2010
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We use frameworks like Ruby on Rails or ProjectTemplate to minimize the time we spend on irrelevant details. By definition, an irrelevant detail isn’t of interest to us. But how can we tell which details are irrelevant? This isn’t a trivial task and it seems to be, on the surface, a profoundly subjective matter. Thankfully,

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Response Times, The Exponential Distribution and Poisson Processes

September 18, 2010
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Response Times, The Exponential Distribution and Poisson Processes

I’m currently reading Luce’s “Response Times”. If you don’t know anything about response times, they are very easily defined: a response time is the length of time it takes a person to respond to a simple request, measured from the moment when the request is made to the moment when the person’s response is recorded.

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The FourierDescriptors Package

September 4, 2010
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The FourierDescriptors Package

Introduction I’ve just uploaded a new package to CRAN based on a stimulus generation algorithm that I use for my experiments on vision. The FourierDescriptors package provides methods for creating, manipulating and visualizing Fourier descriptors, which are a representational scheme used to describe closed planar contours. The canonical reference from the literature is Zahn and

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MCMC Diagnostics in R with the coda Package

August 29, 2010
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MCMC Diagnostics in R with the coda Package

This is a follow up to my recent post introducing the use of JAGS in R through the rjags package. In the comments on that post, Bernd Weiss encouraged me to write a short addendum that describes diagnostic functions that you should use to assess the output from an MCMC sampler. I’ve only been using

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Blegging for Data

August 28, 2010
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I’m in the middle of a new project that involves analyzing the packages that are currently on CRAN. As part of my work, I could really benefit from information about which packages are installed on people’s computers. If you’re willing to part with a bit of your time and privacy, I’d very much appreciate you

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ProjectTemplate

August 26, 2010
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Introduction As many people already know, I’ve recently uploaded a new R package called ProjectTemplate to GitHub and CRAN. The ProjectTemplate package provides a function, create.project(), that automatically builds a directory for a new R project with a clean sub-directory structure and automatic data and library loading tools. My hope is that standardized data loading,

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Using JAGS in R with the rjags Package

August 20, 2010
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Get Everything Set Up I’m going to assume that you have access to a machine that will run JAGS. If you don’t, then you should be able to use WinBUGS, which is very easy to get set up. Unfortunately, the details of what follows may not help you as much if you’re using WinBUGS. To

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Twifficiency Scores

August 18, 2010
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Twifficiency Scores

Neil Kodner wrote a great post this morning about yesterday’s Twifficiency scores outbreak. He grabbed all the auto-tweeted scores he could find and plotted their distribution. I was struck by the asymmetry of the resulting distribution, which you can see below: Thankfully, Neil handed me the raw data for his plot, so I was able

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Unit Testing in R: The Bare Minimum

August 17, 2010
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Introduction This week I decided to start unit testing my R code, so I taught myself the bare minimum about the RUnit and testthat packages to be able to use them. Here’s what I found necessary to get started writing tests with both packages. RUnit Basic Example I’m going to assume that you’ve got a

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