Canterbury Earthquakes part III

As more people keep following the GeoNet website, they are starting to notice the seismic activity in areas other than Christchurch. A few people I've talked to have expressed concern that the Saturday 7-pointer has sparked earthquakes around the country. This is incorrect, as earthquakes below magnitude 3 are extremely common and as can be seen in the plot below, they occur throughout the country. A closer look at the magnitude of these earthquakes shows their temporal distribution is fairly uniform. What is interesting is that prior to the time of the big one there appears to be a lull ...

Julien on R shortcomings

Julien Cornebise posted a rather detailed set of comments (from Jasper!) that I thought was interesting and thought-provoking enough (!) to promote to a guest post. Here it is , then, to keep the debate rolling (with my only censoring being the removal of smileys!). (Please keep in mind that I do not endorse everything stated in this guest post! Especially the point on “Use R!“) On C vs R As a reply to Duncan: indeed C (at least for the bottlenecks) will probably always be faster for the final, mainstream use of an algorithm [e.g. as a distributed R library, ...

Revolution R Enterprise 4.0 free download for academics

The Windows version of our latest enterprise distribution of R, Revolution R Enterprise 4.0, is now being delivered to subscribers and is also available for free download for members of the academic community. Revolution R Enterprise 4.0 is a major update, and includes many new and improved features: Based on R 2.11.1, the current release of the R. See the list of new features in R's language engine since 2.9.2 (upon which the previous release of Revolution R Enterprise was based) in the NEWS file on CRAN. Includes a new package, RevoScaleR, that provides scalable, fast (multicore), and extensible data analysis  for large ...

Embed #rstats Code with Syntax Highlighting on your Blog

If you use blogger or even wordpress you've probably found that it's complicated to post code snippets with spacing preserved and syntax highlighting (especially for R code). I've discovered a few workarounds that involve hacking the blogger HTML template and linking to someone else's javascript templates, but it isn't pretty and I'm relying on someone else to perpetually host and maintain the

Writing a Spatial Function: The Location Quotient

Background: In some cases it is necessary to conduct the same analysis multiple times on either the same or different data. In such circumstances it is worth writing a function to simplify the code. In this example the location quotient provides a simple calculation easily written in to a function. The location quotient (LQ) is an index for comparing a region’s share of a particular activity with the share of that same activity found at a more aggregate spatial level (a good book on this kind of thing is Burt et al.). In this example we take a shapefile of London Boroughs ...

Canterbury Earthquakes part II

Since posting last night, there's been several more aftershocks, including several big ones. The total now stands (at 7:00pm) at 304 aftershocks, 70 greater than 4 on the Richter scale, 29 greater than 4.5, and 10 greater than 5. A couple of the fives happened last night, waking us up, and causing more damage to several buildings around town.This evening's installment is a map of the region of Canterbury where the earthquakes have been centred, showing the epicentre of all aftershocks and their magnitudes. It appears that while smaller tremours have been centred fairly widely, the larger magnitude earthquakes have ...

Confidence Bands for Universal Scalability Models

In the recent GDAT class, confidence intervals (CI) for performance data were discussed. Their generalization to confidence bands (CB) for scalability projections using the USL model also came up informally. I showed a prototype plot but it was an ugly hack. Later requests from GDAT attendees to apply CBs to their own data meant I had to do something about that. I tried a lot of things in R that didn't produce the expected results. Ultimately, I was led to explore the ggplot2 package—the "gg" stands for grammar of graphics. A set of ggplots, corresponding to the VAMOOS stages ...

Truly random?!

Having purchased the September edition of La Recherche because of its (disappointing!) coverage on black matter, I came by a short coverage on an Intel circuit producing “truly random” numbers… I already discussed this issue in an earlier post, namely that there is no reason physical generators are “more” random than congruential pseudo-random generators, but this short paper repeats the same misunderstanding on the role of “random” generators. The paper mentions dangers of pseudo-random generators for cryptography (but this is only when you know the deterministic function and the sequence of seeds used so far), while it misses the essential ...

Gdb Macros for R

When debugging R interactively, one hurdle to navigate is unwrapping SEXP objects to get at the inner data. Gdb has some useful macro functionality that allows you to wrap useful command sequences in reusable chunks. I recently put together the following macro that attempts to extract and print some useful info from a SEXP object. [...]

R Maps

This is an updated version of my Making Maps with R tutorial. I think the code is lot simpler and it also includes some data for you to play around with. Background: Spatial data are becoming increasingly common, as are the tools available in R to process it. Of course one of the best ways of visualizing spatial data is through a map. Maps need to be well thought out. Not least, the selected colours need to be appropriate and sufficient context is provided through the use of a legend, title, scale bar and ...

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