1003 search results for "LaTeX"

R exam

January 30, 2011
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R exam

I spent most of my Saturday perusing R codes to check the answers written by my students to the R exam I gave two weeks ago… The outcome is mostly poor, even though some managed to solve a fair part of the long problem. Except for the few hopeless cases who visibly never wrote a

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ABC model choice not to be trusted [2]

January 27, 2011
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ABC model choice not to be trusted [2]

As we were completing our arXiv summary about ABC model choice, we were helpfully pointed to a recent CRiSM tech. report by X. Didelot, R. Everitt, A. Johansen and D. Lawson on  Likelihood-free estimation of model evidence. This paper is quite related to our study of the performances of the ABC approximation to the Bayes

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ABC model choice not to be trusted

January 26, 2011
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ABC model choice not to be trusted

This may sound like a paradoxical title given my recent production in this area of ABC approximations, especially after the disputes with Alan Templeton, but I have come to the conclusion that ABC approximations to the Bayes factor are not to be trusted. When working one afternoon in Park City with Jean-Michel and Natesh Pillai

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R GUIs, IDEs, and text editors

January 18, 2011
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R GUIs, IDEs, and text editors

When deciding what program to write your R code in it is important to consider a number of factors so you can keep organized and work efficiently.  I found this article useful for getting started.  Text editors include syntax highlightin...

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Introducing Monte Carlo Methods with R [precision]

January 17, 2011
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Introducing Monte Carlo Methods with R [precision]

Doug Rivers, professor of Political Sciences in Stanford, kindly sent me this email yesterday night: The 2nd displayed equation in section 2.1.2 on p. 44 is garbled (it might be interpreted as saying that U and X have the same distribution). I think you intended: And indeed we should have stated the implicit convention that

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When 1 * x != x

January 16, 2011
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When 1 * x != x

Trying to dimly recall things from my maths degree, it seems that in most contexts the whole point of the number one is that it is a multiplicative identity. That is, for any x in your set, 1 * x is equal to x. It turns out that when you move to floating point numbers,

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R: Attack of the hair-trigger bees?

January 12, 2011
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R: Attack of the hair-trigger bees?

In their book “Complex Adaptive Systems”, authors Miller and Page create a theoretic model for bee attacks, based on the real, flying, honey-making, photogenic stingers. Suppose the hive is threatened by some external creature. Some initial group of guard bees sense the danger and fly off to attack. As they go, they lay down a

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Random variable generation (Pt 3 of 3)

January 12, 2011
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Random variable generation (Pt 3 of 3)

Ratio-of-uniforms This post is based on chapter 1.4.3 of Advanced Markov Chain Monte Carlo.  Previous posts on this book can be found via the  AMCMC tag. The ratio-of-uniforms was initially developed by Kinderman and Monahan (1977) and can be used for generating random numbers from many standard distributions. Essentially we transform the random variable of

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Arrogance sampling

January 7, 2011
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Arrogance sampling

A new posting on arXiv by Benedict Escoto on a simulation method for approximating normalising constants (i.e. evidence) with an eye-catching name! Here is the abstract This paper describes a method for estimating the marginal likelihood or Bayes factors of Bayesian models using non-parametric importance sampling (“arrogance sampling”). This method can also be used to

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Le Monde puzzle [52|solution]

January 1, 2011
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Le Monde puzzle [52|solution]

I have now received the first issue of Le Monde magazine, including the solution to puzzle #52 I solved just in time by simulated annealing! The trick is in using the following theorem: Iter(1,x,y) is divisible by 10x-1 if and only if y is divisible by 10x-1. Then the value to be found is divisible

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