Monthly Archives: August 2011

R is a cool image editor #2: Dithering algorithms

August 29, 2011
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R is a cool image editor #2: Dithering algorithms

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); it is slow because I didn't implemented any fasting tricks. It can be easily implemented in C, then used...

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Slides of 10+ talks at R Users Groups

August 29, 2011
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Slides of 10+ talks at R Users Groups

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 →

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Real-time Scoring/Optimization of Predictive Models in R

August 28, 2011
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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...

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Ra vs. compiler package

August 28, 2011
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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...

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HPC for biological research

August 28, 2011
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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 finally took the time to write

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Real-time data collection and analysis in class

August 28, 2011
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Real-time data collection and analysis in class

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 electronic polling technology known as

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Support Vector Machine with GPU

August 27, 2011
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Support Vector Machine with GPU

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...

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Some Additional Thoughts on Useless Averages

Some Additional Thoughts on Useless Averages

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 I want to respond to here.First and foremost, I...

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Forecasting In R: The Greatest Shortcut That Failed The Ljung-Box

August 27, 2011
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Forecasting In R: The Greatest Shortcut That Failed The Ljung-Box

Okay so you want to forecast in R, but don't want to manually find the best model and go through the drudgery of plotting and so on.  I have recently found the perfect function for you.  Its called auto.arima and it automatically fits the bes...

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SIGKDD 2011 Conference — Days 2/3/4 Summary

August 27, 2011
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SIGKDD 2011 Conference — Days 2/3/4 Summary

<< My review of Day 1. I am summarizing all of the days together since each talk was short, and I was too exhausted to write a post after each day. Due to the broken-up schedule of the KDD sessions, I group everything together instead of switching back and forth among a dozen different topics. By far the most enjoyable...

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