Blog Archives

Twins, Tripods and Phantoms at the Comrades Marathon

June 12, 2014
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Twins, Tripods and Phantoms at the Comrades Marathon

Having picked up a viral infection days before this year’s Comrades Marathon, on 1 June I was left with time on my hands and somewhat desperate for any distraction. So I spent some time looking at my archive of Comrades data and considering some new questions. For example, what are the chances of two runners

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Concatenating a list of data frames

June 6, 2014
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It’s something that I do surprisingly often: concatenating a list of data frames into a single (possibly quite enormous) data frame. Until now my naive solution worked pretty well. However, today I needed to deal with a list of over 6 million elements. The result was hours of page thrashing before my R session finally

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Identifying pathways for managing multiple disturbances to limit plant invasions

June 5, 2014
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Andrew Tanentzap, William Lee, Adrian Monks, Kate Ladley, Peter Johnson, Geoffrey Rogers, Joy Comrie, Dean Clarke, and Ella Hayman write: We tested a multivariate hypothesis about the causal mechanisms underlying plant invasions in an ephemeral wetland in South Island, New Zealand to inform management of this biodiverse but globally imperilled habitat. . . . We The post

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Bayesian nonparametric weighted sampling inference

May 28, 2014
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Bayesian nonparametric weighted sampling inference

Yajuan Si, Natesh Pillai, and I write: It has historically been a challenge to perform Bayesian inference in a design-based survey context. The present paper develops a Bayesian model for sampling inference using inverse-probability weights. We use a hierarchical approach in which we model the distribution of the weights of the nonsampled units in the The post

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Race Statistics for Comrades Marathon Novice Runners

May 15, 2014
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Race Statistics for Comrades Marathon Novice Runners

Most novice Comrades Marathon runners finish the race on their first attempt and the majority of them walk (shuffle, crawl?) away with Bronze medals. What is a Novice? To paraphrase the dictionary, a novice is “a person who is new to or inexperienced in the circumstances in which he or she is placed; a beginner”.

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Hazardous and Benign Space Objects: Orbits in the Solar-Ecliptic Reference Frame

May 12, 2014
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Hazardous and Benign Space Objects: Orbits in the Solar-Ecliptic Reference Frame

In two previous posts in this series I have wrangled NEO orbital data into R and then solved Kepler’s Equation to get the eccentric anomaly for each NEO. The final stage in the visualisation of the NEO orbits will be the transformation of locations from the respective orbital planes into a single reference frame. Reference

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Comrades Marathon Negative Splits: The Plot Thickens

May 10, 2014
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Comrades Marathon Negative Splits: The Plot Thickens

I have been thinking a little more about those mysterious negative splits. Not too surprisingly, this thinking happened while I was out running along the Durban beachfront this morning. Let’s have a look at the ten most extreme negative splits from Comrades Marathon 2013: Below are the splits data for these runners (in the same

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Hazardous and Benign Space Objects: Solving Kepler’s Equation

May 8, 2014
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Hazardous and Benign Space Objects: Solving Kepler’s Equation

Following on from my previous post about Near Earth Objects, today we are going to solve Kepler’s Equation to find the eccentric anomaly, which is the next step towards plotting the positions of these NEOs relative to Earth. The Eccentric, True and Mean Anomalies The relationship between the eccentric and true anomalies are depicted in

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Comrades Marathon: Negative Splits and Cheating

May 6, 2014
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Comrades Marathon: Negative Splits and Cheating

With this year’s Comrades Marathon just less than a month away, I was reminded of a story from earlier in the year. Mark Dowdeswell, a statistician at Wits University, found evidence of cheating by some middle and back of the pack Comrades runners. He identified a group of 20 athletes who had suspicious negative splits:

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Hazardous and Benign Space Objects: Getting the Data

April 28, 2014
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Hazardous and Benign Space Objects: Getting the Data

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

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