Blog Archives

Continuous dispersal on a discrete lattice

September 27, 2012
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Continuous dispersal on a discrete lattice

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, it is natural to use

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Mapping Bike Accidents in R

September 14, 2012
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Mapping Bike Accidents in R

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 faced with the problem of seeding the

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The future of Artificial Intelligence – as imagined in 1989

September 6, 2012
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The future of Artificial Intelligence – as imagined in 1989

This image comes from the cover of Preliminary Papers of the Second International Workshop on Artificial Intelligence and Statistics (1989). Someone abandoned it in the lobby of my building at school. Whatever for, I’ll never know. I just love the idea of machine learning/AI/Statistics evoking a robot hand drawing a best fit line through some

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Walmart Invasion

August 26, 2012
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Walmart Invasion

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) epidemic. The video shows monthly

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An update on visualizing Bayesian updating

August 17, 2012
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An update on visualizing Bayesian updating

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 (co-author of Machine Learning for

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The essence of a handwritten digit

August 13, 2012
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The essence of a handwritten digit

If you haven’t yet discovered the competitive machine learning site kaggle.com, 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 hand written digits 0-9. The

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Simulation: The modeller’s laboratory

August 10, 2012
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Simulation: The modeller’s laboratory

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, can offer hypotheses about the

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Olympic body match and 1:1 BMI

August 1, 2012
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Olympic body match and 1:1 BMI

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 Canadian, I exist in an

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Dynamical systems: Mapping chaos with R

July 13, 2012
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Dynamical systems: Mapping chaos with R

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 seeing iid. In ecology, chaotic

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R Workshop: Introducing Slidify – HTML5 slides from R markdown

June 20, 2012
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R Workshop: Introducing Slidify – HTML5 slides from R markdown

Thursday, June 28th, 2012  19h. <–  new evening time! Tomson House: 650 McTavish, H3A 1Y2, Montréal, QC <– new social setting! guRu: Ramnath Vaidyanathan (McGill University) Ramnath Vaidyanathan will introduce the group to slidify, his brand new R package. From the slidify website: “The objective of slidify is to make it easy to create reproducible

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