Publications by Corey Chivers
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 Hackers) piped up on twitter and said that h...
1076 sym 6 img
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 store openings (in red) between 1962 and 2006. ...
840 sym 6 img
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 ...
974 sym 6 img
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 site with some data to draw t...
1794 sym 6 img
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 a contin...
2726 sym R (1872 sym/2 pcs) 8 img
Padding integers for use in filenames
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 with is something like this: results10.txt results11.txt resul...
1351 sym R (405 sym/5 pcs) 6 img
Observing Dark Worlds – Visualizing dark matter’s distorting effect on galaxies
Some people like to do crossword puzzles. I like to do machine learning puzzles. Lucky for me, a new contest was just posted yesterday on Kaggle. So naturally, my lazy Saturday was spent getting elbow deep into the data. The training set consists of a series of ‘skies’, each containing a bunch of galaxies. Normally, these galaxies would exhib...
1846 sym 6 img
Dark matter benchmarks: All over the map
The three benchmark algorithms for predicting the location of dark matter halos are, for the most part, all over the map. Most of the test skies look something like this: There are, however, some skies with rather strong halo signals that get a decent amount of agreement: The Lenstool MLE algorithm is the current state of the art. As such, it�...
949 sym 8 img
Introduction to Bayesian Methods guest lecture
This is a talk I gave this week in Advanced Biostatistics at McGill. The goal was to provide an gentle introduction to Bayesian methodology and to demonstrate how it is used for inference and prediction. There is a link to an accompanying R script in the slides. Related To leave a comment for the author, please follow the link and comment on th...
675 sym 4 img
Introduction to Bayesian lecture: Accompanying handouts and demos
I recently posted the slides from a guest lecture that I gave on Bayesian methods for biologists/ecologist. In an effort to promote active learning, the class was not a straight forward lecture, but rather a combination of informational input from me and opportunities for students to engage with the concepts via activities and discussion of demon...
2012 sym 10 img