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Recently, I had a professor ask me how to take a string and convert it to an R variable name on-the-fly. One possible way is: x [Read more...]

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Ashley put the following comment on Chapter 5 of Introducing Monte Carlo Methods with R”: I am reading chapter 5. I try to reproduced the result on page 128. The R codes don’t work on my laptop. When I try to run the following codes on page 128 __ for (i in 1:(nlm(like,... [Read more...]

If you've been thinking about heading to Chicago in April for the R/Finance conference, here's another reason to go: posting for the committee, Dirk Eddelbuettel announced last week that thanks to a favourable response from sponsors[*], the conference organizers can now offer: a competition for best paper, which given ... [Read more...]

I spend much of my time writing R code for simulations to compare the supervised classification methods that I have developed with similar classifiers from the literature.  A large challenge is to determine which datasets (whether artificial/simulated or real) are interesting comparisons.  Even if we restricted ourselves to multivariate ... [Read more...]

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I have been simulating a lot of data lately  with various covariance (correlation) structures, and one that I have been using is the autocorrelation (or autoregressive) structure, where there is a “lag” between variables. The matrix is a v-dimension matrix of the form $$\begin{bmatrix} 1 & \rho & \rho^2 & \dots & \rho^{v-1}\\ \... [Read more...]

There was a small earthquake in northern England on Tuesday. Barry Rowlingson felt the quake (it rattled the photographs on his wall), but didn't know how big of a quake it was because he didn't know how close he was to the epicentre. The British Geological Survey hadn't yet announced ... [Read more...]

I've recently praised some mainstream media outlets like the New York Times and New Scientist for leading the charge on data journalism. But you don't need to be a large organization to find news in data. With open data sources, and open-source data analysis tools, individuals can make newsworthy discoveries. ... [Read more...]

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The December 20 issue of Forbes magazine, on newsstands now, includes a column about R on page 128 as part of the "Name You Need to Know in 2011" feature. It's basically an excerpt from this blog post by Steve McNally and its comments, and includes quotes from Norman Nie of Revolution Analytics, ... [Read more...]

It is well-known that R has several graphics devices — either the screen devices (X11(), windows(), …) or the off-screen devices (pdf(), png(), …). We can query the default graphics device in options(): getOption('device') In a non-interactive session, the default device is pdf(). This is why Sweave has to create a file ... [Read more...]

Journal Clubs are a great way to learn new research ideas and to keep up with the literature. The idea is that a group of people get together every week or so to discuss a paper of joint interest. This can happen within your own research group or department, or ... [Read more...]

Pierre Jacob and I got this email from a student about our parallel Rao-Blackwellisation paper. Here are some parts of the questions and our answer: Although I understand how the strategy proposed in the paper helps in variance reduction, I do not understand why you set b=1 (mentioned in Section 3.2) ... [Read more...]

Positional bias — the tendency for users to preferentially select results in the first few positions of a search — is a big issue for all kinds of search engines. But for online travel site Orbitz the stakes are higher than for a traditional Web search engine: if a customer chooses the ... [Read more...]

My sabbatical is rapidly coming to an end, and I have to start thinking more and more about teaching. Glancing over my module description for the introductory computational statistics course I teach, I noticed that it’s a bit light on recommend/background reading. In fact it has only two ... [Read more...]

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