Articles by Corey Chivers

Padding integers for use in filenames

September 29, 2012 | Corey Chivers

If you’ve ever written code that generates a whole whack of files, you may have came across the following problem when processing them. Using a naming convention wherein files are numbered will  gum up any ordering which is based on string sorting (ls, for example). What you end up ... [Read more...]

Continuous dispersal on a discrete lattice

September 27, 2012 | Corey Chivers

Dispersal is a key process in many domains, and particularly in ecology. Individuals move in space, and this movement can be modelled as a random process following some kernel. The dispersal kernel is simply a probability distribution describing the distance travelled in a given time frame. Since space is continuous, ... [Read more...]

Mapping Bike Accidents in R

September 14, 2012 | Corey Chivers

At last weekend’s Hack Ta Ville event here in Montreal, I joined up with some talented urban planners and web devs to realize Vélobstacles. The idea of the project is to crowd source information on cycling conditions around the city. As with any crowd sourcing project, we were ... [Read more...]

Walmart Invasion

August 26, 2012 | Corey Chivers

As an invasion biologist, the process of spatial spread is at the heart of what I do. When I came across this dataset of Walmart store openings since 1962 I couldn’t help but see it as an invasion front which looks a lot like a biological invasion or (albeit slow) ... [Read more...]

An update on visualizing Bayesian updating

August 17, 2012 | Corey Chivers

A while ago I wrote this post with some R code to visualize the updating of a beta distribution as the outcome of Bernoulli trials are observed. The code provided a single plot of this process, with all the curves overlayed on top of one another. Then John Myles White (... [Read more...]

The essence of a handwritten digit

August 13, 2012 | Corey Chivers

If you haven’t yet discovered the competitive machine learning site, please do so now. I’ll wait. Great – so, you checked it out, fell in love and have made it back. I recently downloaded the data for the getting started competition. It consists of 42000 labelled images (28×28) of ... [Read more...]

Simulation: The modeller’s laboratory

August 10, 2012 | Corey Chivers

In his 2004 paper in Trends in Ecology and Evolution, Steven Peck argues: Simulation models can be used to mimic complex systems, but unlike nature, can be manipulated in ways that would be impossible, too costly or unethical to do in natural systems. Simulation can add to theory development and testing, ... [Read more...]

Olympic body match and 1:1 BMI

August 1, 2012 | Corey Chivers

In my morning attempt to read the whole internet before beginning work, I came across a program on the BBC website which allows you to see which Olympic athletes are your body doubles. Or rather, which athletes share your height and weight, and therefore your body mass index. Being a ... [Read more...]

Dynamical systems: Mapping chaos with R

July 13, 2012 | Corey Chivers

Chaos. Hectic, seemingly unpredictable, complex dynamics. In a word: fun. I usually stick to the warm and fuzzy world of stochasticity and probability distributions, but this post will be (almost) entirely devoid of randomness. While chaotic dynamics are entirely deterministic, their sensitivity to initial conditions can trick the observer into ... [Read more...]

Simulating Euro 2012

June 11, 2012 | Corey Chivers

Why settle for just one realisation of this year’s UEFA Euro when you can let the tournament play out 10,000 times in silico? Since I already had some code lying around from my submission to the Kaggle hosted 2010 Take on the Quants challenge, I figured I’d recycle it for ... [Read more...]

Distribution of Oft-Used Bash Commands

June 1, 2012 | Corey Chivers

Browsing today, I came across this little one-liner to display which commands I use most often. Here’s what I got: Yep, seems legit. I navigate and look at files a whole bunch (ls, cd, cat), and I do a butt tonne of editing (vim). I sudo like ... [Read more...]

More Bixi Data Visualization

May 17, 2012 | Corey Chivers

I mentioned in a previous post that our team at the recent Hack/Reduce hackathon had some fun with a data set which consisted of Bixi station states at minute level temporal resolution. In addition to pulling out and plotting the flux at each station on an hourly basis, we ...
[Read more...]

R Workshop: Reproducible Research using Sweave for Beginers

April 27, 2012 | Corey Chivers

Monday, April 30, 2012  14h-16h. Stewart Biology Rm w6/12 (Montreal) guRu: Denis Haine (Université de Montréal) Topics Reproducible research was first coined by Pr. Jon Claerbout, professor of geophysics at Stanford University, to describe that the results from researches can be replicated by other scientists by making available data, procedures, ... [Read more...]

Montreal R Workshop: Quantile Regression

April 17, 2012 | Corey Chivers

Stewart Biology Building, McGill University (Rm N4/17) Monday, April 24, 2012  14h-16h Dr. Arthur Charpentier (UQàM) In this workshop we will examine difference concepts related to quantiles, and practical issues based on R codes. This workshop will present quantile regression, and the idea of iterative least square estimation. It will ... [Read more...]

Montreal R Workshop: Introduction to Bayesian Methods

March 22, 2012 | Corey Chivers

Monday, March 26, 2012  14h-16h, Stewart Biology N4/17 Corey Chivers, Department of Biology McGill University This is a meetup of the Montreal R User Group. Be sure to join the group and RSVP. More information about the workshop here. Topics Why would we want to be Bayesian in the first place?  ... [Read more...]
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