Here I implemented in R some dithering algorithms: - Floyd-Steinberg dithering - Bill Atkinson dithering - Jarvis-Judice-Ninke dithering - Sierra 2-4a dithering - Stucki dithering - Burkes dithering - Sierra2 dithering - Sierra3 dithering For each algorithm, I wrote a 2-dimensional convolution function (a matrix passing over a matrix); ... [Read more...]

Links to slides of 10+ talks at R Users Groups in Australia are provided below. Slides of the talks are downloadable at the links, including R codes if any. MelbURN: Melbourne Users of R Network: Experiences with using R in … Continue reading → [Read more...]

I'm working on a 3 part post on how to build, score and perform optimization with predictive models in R. Having done this type of work in IBM SPSS for a number of years, I wanted to replicate it in R. It's amazing how little is published on how to s... [Read more...]

R seems to have two byte code compilers: the Ra add-on module (and the accompanying "jit" package) and the "compiler" package came with the default installation. I wonder how they differentiate from each other and what the strengths and weaknesses... [Read more...]

In early May I had the opportunity to attend a workshop on using high performance computing in R hosted at Nimbios. I’ve been meaning to write a summary of the meeting ever since but got sidetracked by various other projects. Since a collaborator recently asked for meeting notes I ... [Read more...]

As September draws nearer, my mind inevitably turns away from my lofty (and largely unmet) summer research goals, and toward teaching.  This semester I will be trying out a teaching technique using live data collection and analysis as a tool to encourage student engagement.  The idea is based on the ... [Read more...]

Most elementary statistical inference algorithms assume that the data can be modeled by a set of linear parameters with a normally distributed noise component. A new class of algorithms called support vector machine (SVM) remove such constraint. rea... [Read more...]

In my last post, I described three situations where the average of a sequence of numbers is not representative enough to be useful: in the presence of severe outliers, in the face of multimodal data distributions, and in the face of infinite-variance distributions.  The post generated three interesting comments that ... [Read more...]

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As a coincidence, while I was waiting for the solution to puzzle #737 published this Friday in Le Monde, the delivery (wo)man forgot to include the weekend magazine and I had to buy it this morning with my baguette (as if anyone cares!). The solution is (y0,z0,w0)=(38,40,46) and…... [Read more...]

My boss sent me an email (on my day off!) asking me just how much of R is written in the R language.  This is very simple if you use R and a Unix-like system.  It also gives me a good excuse to defend the title of this blog.  It’... [Read more...]

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If you missed this week's webinar, the slides from my presentation Revolution R Enteprise: 100% R and More may be useful as an introduction to R and the additional capabilities of Revolution R Enterprise. The slides themselves and the replay video are also available for download from the link below. Revolution ... [Read more...]

Here's a followup to yesterday's post on using the rdatamarket package to import data into R. Ajay Ohri at the DecisionStats blog offers nine additional methods for bringing data into R, from sources including InfoChimps, the Google Prediction API, the World Bank World Development Indicators, Bloomberg Market Data, and much ... [Read more...]

If the Flight of the Concords taught me anything, it's that you can't trust Australians. This morning I was poking around the DataMarket site, when I noticed something suspicious about Australian sheep production: I decided to investigate further: ju... [Read more...]

In lab known for its quality data collection, high-speed video style, writing the weekly blog post can be a bit of a challenge for the local code monkey. That’s right, no videos today. But lucky for me, even this group … Continue reading → [Read more...]

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Something I’m missing from R (especially coming from Mathematica) is the ability to quickly build interactive graphs, which I find very useful for getting a good intuition of the impact of parameters on a mathematical function. Richie Cotton’s post about … Continue reading → [Read more...]

One of the coolest R packages I heard about at the useR! Conference: Toby Dylan Hocking‘s directlabels package for putting labels directly next to the relevant curves or point clouds in a figure. I think I first learned about this idea from Andrew Gelman: that a separate legend requires ... [Read more...]