Blog Posts by Andrew B. Collier / @datawookie

Hazardous & Benign Objects: Getting the Data

2014-04-28 R

The recent story about a skydiver nearly being hit by falling meteor got me thinking about all the pieces of rock floating around in near-Earth space. Despite the fact that the supposed meteor was probably just a chunk of rock mistakenly packed in with a parachute, the fact that something like that could actually happen is quite intriguing. And not a little frightening.

R Interface to Myfxbook

2014-04-17 R

Myfxbook provides an interface to your FOREX trading accounts as well as an active trading community.

Earthquakes: Land / Ocean Distribution

2014-04-13 R

The next stage in my earthquake analysis project is to partition the events into groups with epicentre over land or water.

Largest Volcanoes & Other Statistics

2014-04-11 R

Around 199 years ago the largest volcano in recorded history, Mount Tambora, erupted, spewing an enormous volume of molten rock and ash into the atmosphere and onto the surrounding land.

Earthquakes: Magnitude / Depth Chart

2014-04-07 R

I am working on a project related to secondary effects of earthquakes. To guide me in the analysis I need a chart showing the location, magnitude and depth of recent earthquakes. There are a host of such charts available already, but since I had the required data on hand, it seemed like a good idea to take a stab at it myself.

Daylight Saving Effect on Financial Indices

2014-04-01 R

Does the transition to and from Daylight Saving Time (DST) have a (significant) effect on the stock market?

Filtering Data with L1 Regularisation

2014-03-27 R regularisation

A few days ago I posted about Filtering Data with L2 Regularisation. Today I am going to explore the other filtering technique described in the paper by Tung-Lam Dao.

Filtering Data with L2 Regularisation

2014-03-25 R regularisation

I have just finished reading Momentum Strategies with L1 Filter by Tung-Lam Dao. The smoothing results presented in this paper are interesting and I thought it would be cool to implement the L1 and L2 filtering schemes in R. We’ll start with the L2 scheme here because it has an exact solution and I will follow up with the L1 scheme later on.

How Long to Conceive?

2014-01-12 R

This morning my wife presented me with a rather interesting statistic: a healthy couple has a 25% chance of conception every month [1], and that this should result in a 75% to 85% chance of conception after a year. This sounded rather interesting and it occurred to me that it really can’t be that simple. There are surely a lot of variables which influence this probability. Certainly age should be a factor and, after a short search, I found some more age-specific information which indicated that for a woman in her thirties, the probability is only around 15% [2,3].

Processing EXIF Data

2013-12-16 R

I got quite inspired by the EXIF with R post on the Timely Portfolio blog and decided to do a similar analysis with my photographic database.

Updated Comrades Winners Chart

2013-12-14 running

On Friday I received my copy of The Official Results Brochure for the 2013 Comrades Marathon. Always makes for a diverting half an hour’s reading. And the tables at the front provide some very interesting statistics. Seemed like a good opportunity to update my Chart of Comrades Winners.

Contour and Density Layers with ggmap

2013-12-14 R

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-Ground Lightning over Houston, Texas”. Geophysical Research Letters 28 (13): 2597–2600.

Amy Cuddy: Your body language shapes who you are

2013-11-27 TED Talk

Amy Cuddy gives a great talk. Provided me with lots to think about and I will happily confess that I have struck a few power poses (but only after ensuring that I am quite alone)!

Deriving a Priority Queue from a Plain Vanilla Queue

2013-11-26 R

Following up on my recent post about implementing a queue as a reference class, I am going to derive a Priority Queue class.

Implementing a Queue as a Reference Class

2013-11-24 R

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 the process. The Implementation We use setRefClass() to create a generator function which will create objects of the Queue class. Read More →

Iterators in R

2013-11-14 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 through the container, one item at a time. Iterators are a fundamental part of contemporary Python programming, where they form the basis for loops, list comprehensions and generator expressions. Read More →

Introduction to Fractals

2013-11-04 R

A short while ago I was contracted to write a short piece entitled “Introduction to Fractals”. Admittedly it is hard to do justice to the topic in less than 1000 words.

Percolation Threshold: Including Next-Nearest Neighbours

2013-11-01 R

Percolation through a larger lattice at the percolation threshold.

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 lattice for various ranges of neighbor links. Below is their illustration of (a) nearest neighbour “NN” and (b) next-nearest neighbour “NNN” links. Read More →

Percolation Threshold on a Square Lattice

2013-10-30 R

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. Percolation has numerous practical applications, the most interesting of which (from my perspective) is the flow of hot water through ground coffee!

Plotting Times of Discrete Events

2013-10-19 R

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.

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