Publications by andrew
Applying an Operation to a List of Variables
Just a quick note on a short hack that I cobbled together this morning. I have an analysis where I need to perform the same set of operations to a list of variables. In order to do this in a compact and robust way, I wanted to write a loop that would run through the variables and apply the operations to each of them in turn. This can be done usin...
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Plotting Times of Discrete Events
I recently enjoyed reading O’Hara, R. B., & Kotze, D. J. (2010). Do not log-transform count data. Methods in Ecology and Evolution, 1(2), 118–122. doi:10.1111/j.2041-210X.2010.00021.x. The article prompted me to think about processes involving discrete events and how these might be presented graphically. I am not talking about counts (which ...
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R package for effect size calculations for psychology researchers
Dan Gerlanc writes: I read your post the other day [now the other month, as our blog is on a bit of a delay] on helping psychologists do research and thought you might be interested in our R package, “bootES”, for robust effect size calculation and confidence interval estimation using resampling techniques. The package provides one function, ...
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Percolation Threshold on a Square Lattice
Manfred Schroeder touches on the topic of percolation a number of times in his encyclopaedic book on fractals (Schroeder, M. (1991). Fractals, Chaos, Power Laws: Minutes from an Infinite Paradise. W H Freeman & Company.). Percolation has numerous practical applications, the most interesting of which (from my perspective) is the flow of hot water ...
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Percolation Threshold: Including Next-Nearest Neighbours
In my previous post about estimating the Percolation Threshold on a square lattice, I only considered flow from a given cell to its four nearest neighbours. It is a relatively simple matter to extend the recursive flow algorithm to include other configurations as well. Malarz and Galam (2005) considered the problem of percolation on a square latt...
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Introduction to Fractals
A short while ago I was contracted to write a short piece entitled “Introduction to Fractals”. The article can be found here. Admittedly it is hard to do justice to the topic in less than 1000 words. Both of the illustrations were created with R. Mandelbrot Set The Mandelbrot Set image was created using the Julia package. library(Julia) Firs...
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Iterators in R
According to Wikipedia, an iterator is “an object that enables a programmer to traverse a container”. A collection of items (stashed in a container) can be thought of as being “iterable” if there is a logical progression from one element to the next (so a list is iterable, while a set is not). An iterator is then an object for moving thro...
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Implementing a Queue as a Reference Class
I am working on a simulation for an Automatic Repeat-reQuest (ARQ) algorithm. After trying various options, I concluded that I would need an implementation of a queue to make this problem tractable. R does not have a native queue data structure, so this seemed like a good opportunity to implement one and learn something about Reference Classes in...
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Deriving a Priority Queue from a Plain Vanilla Queue
Following up on my recent post about implementing a queue as a reference class, I am going to derive a Priority Queue class. Inheritance The syntax for Reference Class inheritance is quite intuitive. PriorityQueue <- setRefClass("PriorityQueue", contains = "Queue", fields = list( ...
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Contour and Density Layers with ggmap
I am busy working on a project which uses data from the World Wide Lightning Location Network (WWLLN). Specifically, I am trying to reproduce some of the results from Orville, Richard E, Gary R. Huffines, John Nielsen-Gammon, Renyi Zhang, Brandon Ely, Scott Steiger, Stephen Phillips, Steve Allen, and William Read. 2001. “Enhancement of Cloud-to...
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