Posts Tagged ‘ mathematics ’

Simple and heuristic optimization

June 29, 2012
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Simple and heuristic optimization

This week, at the Rmetrics conference, there has been an interesting discussion about heuristic optimization. The starting point was simple: in complex optimization problems (here we mean with a lot of local maxima, for instance), we do not ne...

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multiplicitiesoffreedom demonstrates Chaos Theory in Excel. If…

June 29, 2012
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multiplicitiesoffreedom demonstrates Chaos Theory in Excel. If…

multiplicitiesoffreedom demonstrates Chaos Theory in Excel. If he filled in more initial values, you would see a thick bar—like a picture of white-noise. Butterflies flapping their wings in Vermont to change the wind in Hangzhou? A drop of water on ...

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How do I Create the Identity Matrix in R?

June 27, 2012
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How do I Create the Identity Matrix in R?

I googled for this once upon a time and nothing came up. Hopefully this saves someone ten minutes of digging about in the documentation. You make identity matrices with the keyword diag, and the number of dimensions in parentheses. > diag(3) [,...

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How to outrun a crashing alien spaceship

June 11, 2012
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How to outrun a crashing alien spaceship

Hollywood movies are obsessed with outrunning explosions and outrunning crashing alien spaceships. For explosions the movies give the optimal (but unusable) solution: run straight away. For crashing alien spaceships they give the same advice, but in this case it is wrong. We demonstrate the correct angle to flee. Running from a crashing alien spaceship, Prometheus Related posts:

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Nonconvexity, and playing indoor paintball

April 6, 2012
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Nonconvexity, and playing indoor paintball

Following the two previous posts (here and there), on the number of people that don't get wet while playing with water pistols, consider now an indoor version, in a non-convex room (i.e. player behind wall are now, somehow, protected). In the previ...

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Playing with fire (or water)

April 2, 2012
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Playing with fire (or water)

A few days ago, http://www.futilitycloset.com/ published a short post based on the fourth problem of the 1987 Canadian Mathematical Olympiad (from on a problem from the 6th All Soviet Union Mathematical Competition in Voronezh, 1966). The problem i...

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How Not To Draw a Probability Distribution

March 7, 2012
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How Not To Draw a Probability Distribution

If I google for “probability distribution” I find the following extremely bad picture: It’s bad because it conflates ideas and oversimplifies how variable probability distributions can generally be. Most distributions are not unimodal. Most dist...

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Penny pinching yields pennies

January 26, 2012
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Penny pinching yields pennies

A Greek Professor of Economics has written up a thought-provoking series of articles on complexity fetishism. As part of his …Continue reading »

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Random matrix theory and APT’s daily global model

January 25, 2012
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Random matrix theory and APT’s daily global model

Someone emailed me recently and asked about how APT uses random matrix theory in their factor model. Another question I …Continue reading »

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Even odds

January 22, 2012
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Even odds

This evening, I found a nice probabilistic puzzle on http://www.futilitycloset.com/ "A bag contains 16 billiard balls, some white and some black. You draw two balls at the same time. It is equally likely that the two will be the same color as diff...

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