Monthly Archives: April 2010

embed images in Rd documents

April 3, 2010
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The new help system that was introduced in R 2.10.0 and documented in an article of the R journal is very promising. One thing that is planned for future versions of R (maybe 2.12.0) is some way to include images into Rd documents using the fig option of the Sexpr macro Another way is to use data...

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Demonstrating the Power of F Test with gWidgets

April 2, 2010
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e know the real distribution of the F statistic in linear models — it is a non-central F distribution. Under H0, we have a central F distribution. Given 1 – α, we can compute the probability of (correctly) rejecting H0. I created a simple demo to illustrate how the power changes as other parameters vary,

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Because it’s Friday: Chatroulette

April 2, 2010
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Yesterday, Drew Conway posted an analysis of the survival time to events on Chatroulette. If you're familiar with Chatroulette, you'll know what kind of events you can expect to occur when using it. (If you're not, here's a hint: don't try it now if you're at work.) Sadly, it was all an April Fool's Day joke. But Drew takes...

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A free book on Geostatistical Mapping with R

April 2, 2010
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A free book on Geostatistical Mapping with R

Tomislav Hengl of the University of Amsterdam has published new book, A Practical Guide to Geostatistical Mapping. It's jam-packed with 291 pages on mapping and analyzing spatial data using free software including R, SAGA, GRASS, ILWIS and Google Earth, and freely-available map data. The book itself is also available for free, as an Open Access Publication. You can order...

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How to Produce Fake Data Analysis in R: 3 Easy Steps

April 2, 2010
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How to Produce Fake Data Analysis in R: 3 Easy Steps

Did you really think that a team of researchers spent their weekends counting the number of shirtless adolescent men and exposed penises they could find on charoulette.com? Perhaps you should not answer that, as it may be a better measure of your opinion of sociologist than gullibility. It is true, sociologist do say the

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CLT Standard Normal Generator

April 2, 2010
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CLT Standard Normal Generator

I’ve found this standard normal random number generator in a number of places, one of which being from one of Paul Wilmott’s books. The idea is that we can use the Central Limit Theorem (CLT) to easily generate values distributed according to a standard normal distribution by using the sum of 12 uniform random

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Lookup Performance in R

April 2, 2010
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Rumor has it that Joe Adler, author of the O’Reilly Book R in a Nutshell, has joined Linked In as a data scientist.  But that does not keep him from still pumping out some interesting content over at OReilly.com. His latest article is about lookup performance in R. He does a great job giving code

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Opening Statements on Markov Chain Monte Carlo

April 1, 2010
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Opening Statements on Markov Chain Monte Carlo

This quarter I am TAing UCLA’s Statistics 102C. Introduction to Monte Carlo Methods for Professor Qing Zhou. This course did not exist when I was an undergraduate, and I think it is pretty rare to teach Monte Carlo (minus the bootstrap if you count that) or MCMC to undergrads. I am excited about this class because to me, MCMC...

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Frank Harrell’s Regression Modeling Strategies Course Handouts

April 1, 2010
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The previously mentioned Regression Modeling Strategies short course taught by Frank Harrell is nearly over. Here are the handouts (PDF) from the course. Keep an eye out here, I'll be writing a few more posts in the near future on topics Frank covered...

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Quantile LOESS – Combining a moving quantile window with LOESS (R function)

April 1, 2010
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Quantile LOESS – Combining a moving quantile window with LOESS (R function)

In this post I will provide R code that implement’s the combination of repeated running quantile with the LOESS smoother to create a type of “quantile LOESS” (e.g: “Local Quantile Regression”). This method is useful when the need arise to fit robust and resistant (Need to be verified) a smoothed line for a quantile (an example for such a...

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