## Example 7.26: probability question

March 8, 2010
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Here's a surprising problem, from the xkcd blog.Suppose I choose two (different) real numbers, by any process I choose. Then I select one at random (p= .5) to show Nick. Nick must guess whether the other is smaller or larger. Being right 50% of the ...

## R: Eliminating observed values with zero variance

March 8, 2010
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I needed a fast way of eliminating observed values with zero variance from large data sets using the R statistical computing and analysis platform. In other words, I want to find the columns in a data frame that has zero variance. And as fast as possible, because my data sets are large, many, and changing fast....

## R: Eliminating observed values with zero variance

March 8, 2010
By

I needed a fast way of eliminating observed values with zero variance from large data sets using the R statistical computing and analysis platform. In other words, I want to find the columns in a data frame that has zero variance. And as fast as possible, because my data sets are large, many, and changing fast....

## InfoChimps

March 7, 2010
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This looks interesting: http://infochimps.org/search?query=soil

## ggplot and concepts — what’s right, and what’s wrong

March 7, 2010
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A few months back I gave a presentation to the NYC R Meetup. (R is a statistical programming language. If this means nothing to you, feel free to stop reading now.) The presentation was on ggplot2, a popular package for generating graphs of data and statistics. In the talk (which you can see here, including

## A nice link: “Some hints for the R beginner”

March 7, 2010
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Patrick Burns just posted to the mailing list the following massage: There is now a document called “Some hints for the R beginner” whose purpose is to get people up and running with R as quickly as possible. Direct access to it is: http://www.burns-stat.com/pages/Tutor/hints_R_begin.html JRR Tolkien wrote a story (sans hobbits) called ‘Leaf by Niggle’ that has always resonated with me. I...

## One R Tip A Day meets Tecnica Arcana

March 7, 2010
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For italian speaking people only (sorry!). Carlo il curatore dell'ottimo podcast tecnologico Tecnica Arcana mi ha intervistato sulla mia professione e su R. Qui potete scaricare l'intervista in formato mp3.

## Ecological Modelling with “R”

March 7, 2010
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Here i present some Books and Articles about Ecological Modelling and “R”. Since “R” is integrated in Bio7 all the presented methods in the Books and Articles can also be useful together with Bio7. Books: Ellner, Stephen P. & Guckenheimer, John (2006). Dynamic Models in Biology. Princeton University Press Bolker B (2008) Ecological Models and

## Intermarket Whac-A-Mole

March 6, 2010
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Every trader that looks at more than one market throughout the day will recognize that there is a certain symmetrical relationship between certain markets at certain times. The confounding thing about these intermarket relationships is that they are fl...

## schoolmath

March 6, 2010
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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

## Visualizing Drought

March 6, 2010
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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

## 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

## Posterior likelihood

March 6, 2010
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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

## 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.

## 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.

## 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...

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

March 5, 2010
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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...

## GLMM revisted

March 5, 2010
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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...

## R amusements

March 5, 2010
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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

## Example 7.25: compare draws with distribution

March 5, 2010
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In example 7.24, we demonstrated a Metropolis-Hastings algorithm for generating observations from awkward distributions. In such settings it is desirable to assess the quality of draws by comparing them with the target distribution.Recall that the dis...

## Getting data from an image (introductory post)

March 5, 2010
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Hi there! This blog will be dedicated to data visualization in R. Why? Two reasons. First, when it comes to statistics, I am always starting by some exploratory analyses, mostly with plots. And when I handle large quantities of data, it’s nice to make some graphs to get a grasp about what is going on.

## Accessing Climate Change Data and a Custom Panel Function for Filled Polygons

March 4, 2010
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GCS Model Grids Recently finished some collaborative work with Vishal, related to visualizing climate change data for the SEI. This project was funded in part by the California Energy Commission, with additional technical support from the Google Earth Team. One of the final products was an...

## An email about mixtures

March 4, 2010
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As a coincidence, or not, I received the following email just before starting our mixture estimation workshop (the above is Ben Nevis on Monday, whose skyline really looks like a three component mixture!) and giving a discussion on label switching: I am implementing a Markov-Chain Monte Carlo method for Gibbs sampling from a simple mixture

## Yet Another plyr Example

March 4, 2010
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another plyr example quantiles (0.05, 0.25, 0.5, 0.75, 0.95) of DSC by temperature bin There are plenty of good examples on how to use functions from the plyr package. Here is one more, demonstrating how to use ddply with a custom function. Note that there...

## More on the Economist’s special report on big data

March 4, 2010
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I totally missed this the other day, but there's much more to that special report on the data deluge in The Economist. (Thanks to readers SB and DN for pointing this out.) There's an total of nine articles in the report (you can find them all in the Related Items box on this page), including a section on business...

## New Le Monde puzzle

March 3, 2010
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$New Le Monde puzzle$

When I first read Le Monde puzzle this weekend, I though it was even less exciting than the previous one: find and , such that is a multiple of . The solution is obtained by brute-force checking through an R program: and then the a next solution is (with several values for N). However, while

## Quality trimming in R using ShortRead and Biostrings

March 3, 2010
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I wrote an R function to do soft-trimming, right clipping FastQ reads based on quality.This function has the option of leaving out sequences trimmed to extinction and will do left-side fixed trimming as well.#softTrim#trim first position lower than minQuality and all subsequent positions#omit sequences that after trimming are shorter than minLength#left trim to firstBase, (1 implies no left trim)#input:...

## Quality trimming in R using ShortRead and Biostrings

March 3, 2010
By

I wrote an R function to do soft-trimming, right clipping FastQ reads based on quality.This function has the option of leaving out sequences trimmed to extinction and will do left-side fixed trimming as well.#softTrim#trim first position lower than minQuality and all subsequent positions#omit sequences that after trimming are shorter than minLength#left trim to firstBase, (1 implies no left trim)#input:...