Publications by andrew
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: > split.ratio.2013 = subset(split.ratio, year == 2013) > # > split.ratio....
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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 Frame The heliocentri...
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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”. In the context of the Comrade...
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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 i...
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Identifying pathways for managing multiple disturbances to limit plant invasions
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 ha...
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Concatenating a list of data frames
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 surrendered. I suppose I s...
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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 passing through halfway and the fini...
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Comment of the week
This one, from DominikM: Really great, the simple random intercept – random slope mixed model I did yesterday now runs at least an order of magnitude faster after installing RStan 2.3 this morning. You are doing an awesome job, thanks a lot! The post Comment of the week appeared first on Statistical Modeling, Causal Inference, and Social Scienc...
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Stan goes to the World Cup
I thought it would be fun to fit a simple model in Stan to estimate the abilities of the teams in the World Cup, then I could post everything here on the blog, the whole story of the analysis from beginning to end, showing the results of spending a couple hours on a data analysis. It didn’t work so well, but I guess that’s part of the story t...
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Comrades Marathon: A Race for Geriatrics?
It has been suggested that the average Comrades Marathon runner is gradually getting older. As an “average runner” myself, I will not deny that I am personally getting older. But, what I really mean is that the average age of all runners taking part in this great event is gradually increasing. This is not just an idle hypothesis: it is suppor...
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