Monthly Archives: March 2010

schoolmath

March 6, 2010
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schoolmath

In connection with the Le Monde puzzle of last week, I was looking for an R function that would give me the prime factor decomposition of any integer. Such a function exists within the package schoolmath, developped by Joerg Schlarmann and Josef Wienand. It is called prime.factor and it returns the prime factors of any

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Visualizing Drought

March 6, 2010
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Visualizing Drought

The impacts of drought depend on time-scale. On short time-scales, drought means dry soil. On long time-scales, it means dry rivers and empty reservoirs. A region may simultaneously experience dry conditions on one time-scale and wet conditions on another e.g. wet soil but low streamflow or visa versa. Standardized Precipitation Index (SPI) is a widely

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Contingency Tables – Fisher’s Exact Test

March 6, 2010
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A contingency table is used in statistics to provide a tabular summary of categorical data and the cells in the table are the number of occassions that a particular combination of variables occur together in a set of data. The relationship between variables in a contingency table are often investigated using Chi-squared tests. The simplest contingency

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Posterior likelihood

March 6, 2010
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Posterior likelihood

At the Edinburgh mixture estimation workshop, Murray Aitkin presented his proposal to compare models via the posterior distribution of the likelihood ratio. As already commented in a post last July, the positive aspect of looking at this quantity rather than at the Bayes factor is that the priors are then allowed to be improper if

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oro.nifti 0.1.3

March 5, 2010
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The R package oro.nifti has been released.  Medical imaging data, in NIfTI or Analyze formats, may be input, created from scratch, converted from DICOM (using oro.dicom) and output to a file. 

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oro.nifti 0.1.3

March 5, 2010
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The R package oro.nifti has been released.  Medical imaging data, in NIfTI or Analyze formats, may be input, created from scratch, converted from DICOM (using oro.dicom) and output to a file. 

Read more »

InformationWeek on Urlocker

March 5, 2010
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InformationWeek published today a profile of Zack Urlocker, the former MySQL executive who recently joined REvolution's board: Former MySQL staffer Zack Urlocker is going to try to do for predictive analytics what he once did for relational database systems: bring open source code to a user population that hasn't necessarily had access to the technology before. REvolution Computing of...

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Because it’s Friday: Why a Salad Costs More than a Big Mac

March 5, 2010
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Because it’s Friday: Why a Salad Costs More than a Big Mac

In the US, at least. Via The Consumerist: Incidentally, the US FDA doesn't publish pyramids like this any more: it's now a garish personalized 2-d triangle with stripes. But at least it doesn't make the error of dimension committed by the left-hand pyramid: that orange section is a hell of a lot larger than 74% of the volume. The...

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GLMM revisted

March 5, 2010
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GLMM revisted

A short while ago, I reported some discrepancies between the results produced by "lme4" and other R packages as well as Stata. Today I upgraded to the most recent version of "lme4a" and re-ran my model. The error of false convergence disappea...

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R amusements

March 5, 2010
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R amusements

On a lark, and to kill a bit of time, I was running the R fortune command looking for references to SAS. Here’s what two successive random fortunes turned up. Can there be two more antipodal opinions about the same product? I laughed out loud. > fortune(‘SAS’) There are companies whose yearly license fees to

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