Monthly Archives: September 2010

How to generate correlated random numbers

September 1, 2010
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We've covered how to generate random numbers in R before, but what if you want to go beyond generating one random number at a time? What if you want to generate two, or three or more random numbers, and what's more, you want them to be correlated? JD Long lays out the way in a couple of posts at...

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Random dive MH

September 1, 2010
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Random dive MH

A new Metropolis-Hastings algorithm that I would call “universal” was posted by Somak Dutta yesterday on arXiv. Multiplicative random walk Metropolis-Hastings on the real line contains a different Metropolis-Hastings algorithm called the random dive. The proposed new value x’ given the current value x is defined by when is a random variable on . Thus,

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How to check if a file exists with HTTP and R

September 1, 2010
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How to check if a file exists with HTTP and R

So, there’s probably an easier way to do this (please let me know if you know it)… Suppose you’re working with a system which creates (binary) files and posts them for download on a website. You know the names of the files that will be created. However, they may not have been made yet (they’re

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Is this good or bad programming?

September 1, 2010
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If I come across this kind of code when I'm checking (QCing) code it makes me want to punch the programmer's face. I find that it's impossible to step through and check each dataset with the previous incarnation. Which is how I check what h...

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apply() function and ABM in R

September 1, 2010
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I know know...I've been away again...We (myself and Mark Lake) are presenting a paper at the CECD conference and we have still some to stuff to finish...so I'm really, really busy... I'll post asap a much more detailed post on the conference and o...

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apply() function and ABM in R

September 1, 2010
By

I know know...I've been away again...We (myself and Mark Lake) are presenting a paper at the CECD conference and we have still some to stuff to finish...so I'm really, really busy... I'll post asap a much more detailed post on the conference and o...

Read more »

Monte Carlo testing of classification groups

September 1, 2010
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This is another article on the theme of defining groups in a hierarchical classification. A previous article described homogeneity analysis to visualize how any well any number of groups, defined at the same level accounts for the variability in the dataset, as measured by within-group pairwise distances. Here we will look at testing whether splitting a particular group...

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Monte Carlo testing of classification groups

September 1, 2010
By
Monte Carlo testing of classification groups

This is another article on the theme of defining groups in a hierarchical classification. A previous article described homogeneity analysis to visualize how any well any number of groups, defined at the same level accounts for the variability in the da...

Read more »