How to estimate PI when we only have R and the formula for the surface of a circle (Surface = PI * r * r)?The estimation of this number has been one of the greatest challenge in the history of mathematics. PI is the ratio between a circle's circumferen... [Read more...]

[Updated 10/18/2012: Fixed a typo in which mantissa was replaced with exponent.] Over the weekend, Viral Shah updated Julia’s implementation of randn() to give a 20% speed boost. Because we all wanted to test that this speed-up had not come at the expense of the validity of Julia’s RNG system, ... [Read more...]

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In honor of today’s announcement of the Nobel Prize for Roth and Shapley, I found an illustration of the deferred acceptance algorithm from 1962 in R. Credit for the code goes to the blogger at Letters from London, and I’ve included a Gi... [Read more...]

This week, we look at plotting data using scatterplots. I'll definitely have a post on other ways of plotting data, like boxplots or histograms.Our data from last week remains the same:First, a quick way to look at all of your continuous variables at once is just to do ... [Read more...]

When it comes down to it R does a really good job handling structured data like matrices and data frames. However, its ability to work with unstructured data is still a work in progress. It can and it does handle text mining but the documentation is incomplete and the capabilities ... [Read more...]

Compressed sensing (CS) is pretty much appealing all current signal processing research community. At the same time, popularity of R language gaining a strong foot in the research and industry. Even though historically MATLAB is a de-facto standard in ... [Read more...]

The authors are Andrie de Vries and Joris Meys. Executive summary Pretty much all I’d hoped for — and I had high hopes. Significance The “Dummies” series is popular for introducing specific topics in an inviting way. R For Dummies is a worthy addition to the pack. There is a ... [Read more...]

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As often happens, I have learned of a technique just as it is being called into question. In this case, the technique is changing the aspect ratio of a line plot such that the typical slope of each segment is 45° (see), a rule of thumb which has bee... [Read more...]

I love good typography, even more so as Microsoft Word and PowerPoint have debased our standards. When I see a really fine piece of technical typesetting, it’s almost always done using TeX and friends. Beautiful LaTeX documents are easy to … Continue reading → [Read more...]

One of the most widely seen FAQ coming across list serves and R help sites is the question: “How do I re-arrange/re-order (plotting geom/aesthetic such as bar/labels) in a (insert plot type here) using(insert graphics system here) in R?” . … Continue reading → [Read more...]

Problem When a correlation or covariance matrix is not positive definite (i.e., in instances when some or all eigenvalues are negative), a cholesky decomposition cannot be performed. Sometimes, these eigenvalues are very small negative numbers and occur due to rounding or due to noise in the data. In simulation ... [Read more...]

The gridSVG package exports grid images to an SVG format for viewing on the web. This article describes a new development in the way that gridSVG produces the SVG output. The result is greater flexibility in how the SVG output … Continue reading → [Read more...]

Rcpp release 0.9.15 is now on CRAN and being uploaded to Debian. Martin Morgan provided a clever fix for a header search needed between clang++ (especially on OS X) and g++ (which still provided libstdc++ and headers for clang++). This should hopefu... [Read more...]

I gave a very brief 10mn introduction to ggplot2 at the Birmingham R user group meeting on Monday. The aim was to give a headstart to R users who’ve heard of ggplot2 but never got around to trying it. I … Continue reading → [Read more...]

In this post the football model is programmed into JAGS. There are all the reasons to do so. Jags 3.3 is recently released, I was stimulated by Gianluca's post . Obviously I could copy the model in his paper, but that would be too easy a... [Read more...]

The three benchmark algorithms for predicting the location of dark matter halos are, for the most part, all over the map. Most of the test skies look something like this: There are, however, some skies with rather strong halo signals that get a decent amount of agreement: The Lenstool MLE ... [Read more...]

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Some people like to do crossword puzzles. I like to do machine learning puzzles. Lucky for me, a new contest was just posted yesterday on Kaggle. So naturally, my lazy Saturday was spent getting elbow deep into the data. The training set consists of a series of ‘skies’, each containing ... [Read more...]