Articles by Matt Shotwell

HRSA Area Resource File Format 2009

February 23, 2011 | Matt Shotwell

From the HRSA website: [The ARF 2009] is a database containing more than 6,000 variables for each of the nation’s counties. ARF contains information on health facilities, health professions, measures of resource scarcity, health status, economic activity, health training programs, and socioeconomic and environmental characteristics. The data file itself is formatted ... [Read more...]

Where’s your high-end sportswear made?

February 13, 2011 | Matt Shotwell

Sierra Trading Post mailed me their End-of-Winter 2011 catalog, which consists mostly of mid- to high-end sportswear products, but also things like snow skis, flashlights, and binoculars. STP sells closeouts, overstock, seconds, and items with cosmetic blemishes or irregularities. I spent an hour of relaxation time enumerating the various product brands ... [Read more...]

The Automatic Millionaire & Amortization

January 8, 2011 | Matt Shotwell

Dan Byrne of Vanderbilt University gave me a book back in October titled The Automatic Millionaire by David Bach. The book is an easy read and full of sound advice that I intend to take. Bach espouses a plan for retirement built on the principles of “paying yourself first” (i....
[Read more...]

Bayesian Diabetes Projections by CDC

October 22, 2010 | Matt Shotwell

Bayesian methods are supporting decisions and news at the national level! The Centers for Disease Control and Prevention summarizes a report published in the journal Population Health Metrics. The news also made it to the national media. The report (JP Boyle, TJ Thompson, EW Gregg, LE Barker, and DF Williamson (2010) “...
[Read more...]

A Not Quite Random Number Generator (NQRNG)

September 13, 2010 | Matt Shotwell

I connected the instrumentation amplifier described in an earlier post to a piezoelectric transducer (buzzer) and made recordings at 5000 gain. The plot below shows 1000 such measurements over 1.0 seconds. There is a 4.0 second (at 1000Hz) sample of the data here piezo.csv. There is a clear sinusoidal signal in these data ... [Read more...]

ECG Project

September 8, 2010 | Matt Shotwell

In an earlier post, I described some ECG signal processing. In fact, these recordings were from my own heart, and I had collected them using a homemade ECG. The following is a repost from my old site describing the device. I assembled an instrumentation amplifier to measure cardiac potentials (i.... [Read more...]

Eigenimages: The AT&T Cambridge Faces Database

September 7, 2010 | Matt Shotwell

I picked up the AT&T Laboratories Cambridge database of faces for a clustering application. The database consists of images of 40 distinct subjects, each in 10 different facial positions and expressions. Typically, the goal of clustering in these data is to recover the ‘true’ partition, or that which isolates images of ... [Read more...]

Tools for Hacking R: Git + Subversion

August 24, 2010 | Matt Shotwell

In an earlier post, I discussed how to use Subversion to download, edit, and generate a patch against R‘s source code. Since most of us can’t commit our code changes back to R‘s repository, we can consider alternatives to store and maintain our patch, until it is ... [Read more...]

Tools for Hacking R: Subversion

August 23, 2010 | Matt Shotwell

The development version of R is stored in a Subversion repository at the URL In fact, you can browse the source code by clicking the link. Subversion Hierarchy Subversion is software for source code revision control. That means it keeps track of changes, who ... [Read more...]

Ed Burnette on Software Patents

August 17, 2010 | Matt Shotwell

Ed Burnette makes a point that hits home, with regard to software patents, and how engineers and programmers of modern companies are now being asked to write them: Unfortunately, the joke is on all of us. It’s on our economy, as we let patents choke down innovation and increase ... [Read more...]

R Environments for Gibbs Sampler State

August 10, 2010 | Matt Shotwell

I recently decided to revisit some R code that implements a Gibbs sampler in an attempt to decrease the iteration time. My strategy was to implement the sampler state as an R environment rather than a list. The rationale was that passing an environment to and from functions would reduce ... [Read more...]

A tty Connection for R

July 26, 2010 | Matt Shotwell

I completed (some time ago) an initial version of a patch for R, version 2.11.1, that adds a POSIX tty connection. The patch is confirmed to compile and works on Mac OS X (thanks to Ashwin Bhat of Georgia Tech) and Debian GNU Linux. However, it should be portable to other ... [Read more...]

Documenting R‘s Connections Internals

July 16, 2010 | Matt Shotwell

In studying R‘s connections source code, I’ve put together a series of notes about their workings. Rather than let the notes go where most of my notes go (I have no idea ), I decided to do some proofreading and make the notes available to others who might be ... [Read more...]

Short Open Source Q&A with Revolution Analytics

July 14, 2010 | Matt Shotwell

I recently e-mailed David Smith of Revolution Analytics with a few questions about their relationship with the R-project, and how they handle R‘s source code. David mentioned, and I’m flattered that my email motivated an additional page on the Revolution website. Beyond this, I have no other relationship ... [Read more...]

Funny Math in Governor Approval Ratings

July 9, 2010 | Matt Shotwell

Andrew Gelman wrote today about some erroneous U.S. Governor approval ratings, noting that the ratings for Janet Napolitano sum to 108%. In fact most of these ratings do not sum to 100%. I prepared a clean CSV file of the ratings, making use of R‘s XML library and the readHTMLTable ... [Read more...]

ASCII Scatterplots in R

June 25, 2010 | Matt Shotwell

I really like R‘s stem function, it creates a stem-and-leaf plot right in the R console, no fancy graphics devices required! In a recent R-help post, Ralf Bierig presented a very nice ASCII scatterplot representing two densities. Unfortunately, I don’t know of any R function that will generate ... [Read more...]

More powerful iconv in R

June 19, 2010 | Matt Shotwell

The R function iconv converts between character string encodings, for example, from the locale dependent encoding to UTF-8: __ iconv("foo", to="UTF-8") [1] "foo" However, R has long-running trouble with embedded null characters ('') in strings. Hence, if we try to convert to an encoding that permits embedded null characters, iconv ... [Read more...]

R-help follow-up: truncated exponential

June 16, 2010 | Matt Shotwell

I recently posted the message below with regard to sampling from the truncated exponential distribution. I left out the derivation of the CDF (mostly because text math is ugly), so I’ve included it here. There is also a short JSS article about truncated distributions in R. This problem in ... [Read more...]
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