programming

Computational Statistics

May 9, 2010 | xi'an

Do not resort to Monte Carlo methods unnecessarily. When I received this 2009 Springer-Verlag book, Computational Statistics, by James Gentle a while ago, I briefly took a look at the table of contents and decided to have a better look later… Now that I have gone through the whole book, I ...
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hash-2.0.0

April 30, 2010 | Christopher Brown

Come see my talk on hashes in R at useR! 2010. (http://user2010.org/) July 20-23 National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, USA [Read more...]

Experiments with igraph

April 21, 2010 | nsaunders

Networks – social and biological – are all the rage, just now. Indeed, a recent entry at Duncan’s QOTD described the “hairball” network representation as the dominant cultural icon in molecular biology. I’ve not had occasion to explore networks “professionally”, but have always been fascinated by both networks and the ...
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R is an Epic Fail?

April 15, 2010 | Yihui Xie

I came across this blog post just now: The Next Big Thing, and of course these words caught my attention: [...] However, for me personally and for most users, both individual and organizational, the much greater cost of software is the time it takes to install it, maintain it, learn it ... [Read more...]

Plotting “time of day” data using ggplot2

April 14, 2010 | nsaunders

William asks: How can I make a graph that looks like this, “tweet density” style, showing time intervals? He then helpfully describes his input data: a CSV file with headers “time started, time finished, date”. Here’s a simple CSV file, tasks.csv: task,date,start,end task1,2010-03-05,09:00:00,13:00:00 ... [Read more...]

Seamless R Extensions using Rcpp and RInside

April 7, 2010 | Drew Conway

I just added a new video to the R repository, and this one comes from the Los Angeles R Meetup. The folks in LA were fortunate enough to have Dirk Eddelbuettel—renowned R expert and StackOverflow super-user—discuss his joint work with Romain François for interfacing C++ and R ... [Read more...]

Matrix determinant with the Lapack routine dspsv

April 6, 2010 | Matt Shotwell

The Lapack routine dspsv solves the linear system of equations Ax=b, where A is a symmetric matrix in packed storage format. However, there appear to be no Lapack functions that compute the determinant of such a matrix. We need to compute the determinant, for instance, in order to compute ... [Read more...]

BioMart (and biomaRt)

March 26, 2010 | nsaunders

I’ve been vaguely aware of BioMart for a few years. Inexplicably, I’ve only recently started to use it. It’s one of the most useful applications I’ve ever used. The concept is simple. You have a set of identifiers that describe a biological object, such as a ... [Read more...]

ECG Signal Processing

March 24, 2010 | Matt Shotwell

After reading (most of) “The Scientists and Engineers Guide to Digital Signal Processing” by Steven W. Smith, PhD, I decided to take a second crack at the ECG data. I wrote a set of R functions that implement a windowed (Blackman) sinc low-pass filter. The convolution of filter kernel with ...
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A Case Study in Optimising Code in R

February 16, 2010 | Jeromy Anglim

This post presents an experience I had optimising the efficiency of code for a data analysis task in R. I'm not an expert in programming nor code optimisation. However, I thought my experience might make an interesting case study for others at a simila...
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A new twist on the identifier mapping problem

January 11, 2010 | nsaunders

Yesterday, Deepak wrote about BridgeDB, a software package to deal with the “identifier mapping problem”. Put simply, biologists can name a biological entity in any way that they like, leading to multiple names for the same object. Easily solved, you might think, by choosing one identifier and sticking to it, ... [Read more...]

[, [[, $: R accessors explained

October 21, 2009 | Christopher Brown

For more than ten years, I have been teaching R both formally and informally. One thing that I find often trips up students is the use of R’s accessors and mutators. ( For those readers not from a formal computer science background, an accessor is a method for accessing data ...
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R and data

May 26, 2009 | erehweb

My fellow bloggers John and Scott have posted recently about the free statistical programming language R.  How does it compare to an expensive language like SAS? If you’ve done any statistical analysis, then you’ll know that getting and cleaning the data is a major step in any project.  ... [Read more...]

S3 vs S4, efficiency issues

May 23, 2008 | Michal

While developing some new simulation code with S4 system I stumbled upon some big difficulties in terms of computational efficiency. That lead me to diging into archives of Rhelp and Rdevel looking for clues. I found some interesting threads that address almost exactly the same problems that I do. Read ... [Read more...]
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