Blog Archives

Comrades Marathon Finish Predictions

April 23, 2015
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Comrades Marathon Finish Predictions

* If you see a bunch of errors, you might want to try opening the page in a different browser. I have had some trouble with MathJax and Windows Explorer. There are various approaches to predicting Comrades Marathon finishing times. Lindsey Parry, for example, suggests that you use two and a half The post

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A Sankey Plot with Uniform Coloured Edges

April 7, 2015
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A Sankey Plot with Uniform Coloured Edges

Following up on my previous post about generating Sankey plots with the riverplot package. It's also possible to generate plots which have constant coloured edges. Here's how (using some of the data structures from the previous post too): The post A Sankey Plot with Uniform Coloured Edges appeared first on Exegetic Analytics.

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Bags, Balls and the Hypergeometric Distribution

April 3, 2015
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Bags, Balls and the Hypergeometric Distribution

A friend came to me with a question. The original question was a little complicated, but in essence it could be explained in terms of the familiar urn problem. So, here's the problem: you have an urn with 50 white balls and 9 black balls. The black balls are individually numbered. Balls are drawn from The post

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Bags, Balls and the Hypergeometric Distribution: Update

April 2, 2015
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So... the Hypergeometric distribution (as used in one of my previous posts). That was a bit of overkill, wasn't it? To recap the problem: we have an urn filled with a selection of white and black balls. We want to calculate the probability that all of the white balls and all but one of the The post

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The Price of Fuel: How Bad Could It Get?

April 1, 2015
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The Price of Fuel: How Bad Could It Get?

The cost of fuel in South Africa (and I imagine pretty much everywhere else) is a contentious topic. It varies from month to month and, although it is clearly related to the price of crude oil and the exchange rate, various other forces play an influential role. According to the Department of Energy the majority The post

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Dealing with a Byte Order Mark (BOM)

March 11, 2015
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Dealing with a Byte Order Mark (BOM)

I have just been trying to import some data into R. The data were exported from a SQL Server client in tab-separated value (TSV) format. However, reading the data into R the "usual" way produced unexpected results: Those weird characters in the first record... where did they come from? They don't show up in a The post

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Book Review: R for Business Analytics

January 28, 2015
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Book Review: R for Business Analytics

The book R for Business Analytics by Ajay Ohri sets out to look at "some of the most common tasks performed by business analysts and helps the user navigate the wealth of information in R and its 4000 packages." In my opinion it succeeds in covering an extensive range of topics but fails to provide The post

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Downloading Option Chain Data from Google Finance in R: An Update

January 13, 2015
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Downloading Option Chain Data from Google Finance in R: An Update

I recently read an article which showed how to download Option Chain data from Google Finance using R. Interestingly, that article appears to be a close adaption of another article which does the same thing using Python. While playing around with the code from these articles I noticed a couple of things that might benefit

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Simulating Intricate Branching Patterns with DLA

December 16, 2014
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Simulating Intricate Branching Patterns with DLA

Manfred Schroeder's book Fractals, Chaos, Power Laws is a fruitful source of interesting topics and projects. He gives a thorough description of Diffusion-Limited Aggregation (DLA) as a technique for simulating physical processes which produce intricate branching structures. Examples, as illustrated below, include Lichtenberg Figures, dielectric breakdown, electrodeposition and Hele-Shaw flow. Diffusion-Limited Aggregation DLA is conceptually

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Zacks Data on Quandl

November 8, 2014
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Zacks Data on Quandl

Data from Zacks Research have just been made available on Quandl. Registered Quandl users have free preview access to these data, which cover the following: Earnings Estimates: forward-looking consensus forecasts; Earnings Surprises: estimated future and actual historical earnings; Earnings Announcements: predictions for earnings announcement dates, parameters, and supplementary data; Sales Estimates: analogous to earnings estimates,

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