Monthly Archives: May 2011

Example 8.37: Read sheets from an excel file

May 11, 2011
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Example 8.37: Read sheets from an excel file

Microsoft Excel is an awkward tool for data analysis. However, it is a reasonable environment for recording and transfering data. In our consulting practice, people frequently send us data in .xls (from Excel 97-2003) or .xlsx (from Excel 2007 or 201...

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sab-R-metrics: Basics of LOESS Regression

May 11, 2011
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sab-R-metrics: Basics of LOESS Regression

Last week, I left you off at logistic regression. This week, I'll be pushing the limits of regression analysis a bit more with a smoothing technique called LOESS regression. There are a number of smoothing methods that can be used, such as Smoothing ...

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One-way ANOVAs in R – including post-hocs/t-tests and graphs

May 11, 2011
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One-way ANOVAs in R – including post-hocs/t-tests and graphs

In this post, I go over the basics of running an ANOVA using R. The dataset I’ll be examining comes from this website, and I’ve discussed it previously (starting here and then here). I’ve not seen many examples where someone runs through the … Continue reading →

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Multivariate probit regression using (direct) maximum likelihood estimators

May 11, 2011
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Multivariate probit regression using (direct) maximum likelihood estimators

Consider a random pair of binary responses, i.e. with taking values 1 or 2. Assume that probability can be function of some covariates . The Gaussian vector latent structure A standard model is based a latent Gaussian structure, i.e. there exi...

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EC2 Trials and Tribulations, Part 1 (Web Crawling)

May 11, 2011
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EC2 Trials and Tribulations, Part 1 (Web Crawling)

Elastic Compute Cloud (EC2) is a service provided a Amazon Web Services that allows users to leverage computing power without the need to build and maintain servers, or spend money on special hardware. The idea is simple, the user “boots” up one or more machines and then accesses those machines as if they were logged into any other machine...

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An essential vocabulary for the R language

May 11, 2011
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The Oxford English Dictionary includes more than 600,000 words, yet most of us get by in our day-to-day lives with a vocabulary of just a few thousand. In a similar vein, the R language includes thousands of functions: when you start up R 2.13, you have 2832 functions at your disposal: > length(apropos(".", mode="function")) 2382 This includes only...

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Comparison of functions for comparative phylogenetics

May 11, 2011
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Comparison of functions for comparative phylogenetics

With all the packages (and beta stage groups of functions) for comparative phylogenetics in R (tested here: picante, geiger, ape, motmot, Liam Revell's functions), I was simply interested in which functions to use in cases where multiple functions exis...

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Defining Custom Model Priors in BMS

Bayesian Model Averaging (BMA) allows for any kind of model prior distributions. While the R package BMS has built-in support for several types of commonly used priors, there may be the need for constructing a custom model prior in a particular exerci...

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A clock utility, via console hackery

May 11, 2011
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A clock utility, via console hackery

A discussion on StackOverflow today shows an interesting use of special characters inside the cat function. The most common special characters that you may have come across are the tab and newline characters, represented by \t and \n respectively. Try them for yourself. cat("Red\tlorry\nYellow\tlorry\n") cat also respects the backspace character, \b, and the carriage return

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High Low Clustering on intraday high frequency sampled data

May 10, 2011
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High Low Clustering on intraday high frequency sampled data

Nothing unusually exciting on this post, but I happened to be engaged in some particle based methods recently and made some simple visual observations as I was setting up some of the sampling environment in R.  I am also using Rkward and Ubuntu to...

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