Here are our slides for the ABC [very] short course Jean-Michel and I give at ISBA 2014 in Cancún next Monday (if your browser can manage Slideshare…) Although I may switch the pictures from Iceland to Mexico, on Sunday, there will be not much change on those slides we both ... [Read more...]

In the following post I will map out some item information functions for item response theory (IRT) models using the common 3 parameter logistic model for binary responses. The model takes three parameters (obviously) which relate to the item features ... [Read more...]

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As announced by Peter Dalgaard for the R Core Team today, R 3.1.1 has been released. Codenamed "Sock it to Me", this is a patch release for R 3.1, and mostly includes minor bug fixes. It also includes some small improvements, including easier access to package help files, improved accuracy when importing ... [Read more...]

A question came up about regarding Q1.4.9 in Cherney, Denton, Waldron. Here is a snippet of the original question: Consider …Continue reading → [Read more...]

Purchases are choices from available alternatives. Post-purchase, we know what is the most preferred, but all the other options score the same. Regardless of differences in appeal, all the remaining items received the same score of not chosen. A second... [Read more...]

I've done a few posts on Syria and have used data provided by the UNHCR for different analysis or visualization.  There are several links on their Syrian refugee data portal that communicate the breadth of this crisis numerically and vis... [Read more...]

Today's exercise is another nice and simple one, and allows you to get used to manipulating datasets in R.Exercise 4 - How to read a file of coordinate data into R and make sure it is numeric.Reading your data files into R  for anal... [Read more...]

by Joseph Rickert John Chambers opened UseR! 2014 by describing how the R language grew out of early efforts to give statisticians easier access to high quality statistical software. In 1976 computational statistics was a very active field, but most algorithms were compiled as Fortran subroutines. Building models with this software was ... [Read more...]

In our last blog post we announced the addition of GitHub and  Bioconductor R packages to Rdocumentation. For the more technical amongst you, I’ll give a short, high-level description of what’s under the hood at Rdocumentation. Along with that I’ll zoom in on some of the challenges ... [Read more...]

In case you missed them, here are some articles from June of particular interest to R users: The useR! 2014 conference in Los Angeles opened with 16 tutorials. DataInformed published an article by David Smith on how various companies use R. Joe Rickert reviews the new book "Applied Predictive Modeling" by Max ... [Read more...]

This post examines an n-day median filter for two desirable properties: robustness to outliers and an inherent trend-confirming lag. While … Continue reading → [Read more...]

I recently found myself a bit stuck. I needed to cluster some data. The distances between the data points were not representable in Euclidean space so I had to use hierarchical clustering. But then I wanted stable clusters that would retain their shape as I updated the data set with ... [Read more...]

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One of the features of Rcpp11 people seemed to like during useR is the fuse function. fuse is somewhat similar to the c function in R. For the purpose of this post, let's simplify what fuse does, and just say that it takes several compatible vector... [Read more...]

John Hauser, because no one questions his expertise, is an excellent spokesperson for the viewpoint that consumer preferences are real, as presented in his article "Self-Reflection and Articulated Consumer Preferences." Simply stated, preferences are e... [Read more...]

I use rolling and running functions almost daily with financial time series. In my post A Whole New World with Chains and Pipes, I made this statement I have noticed that rolling analysis with xts can sometimes be slow. as.matrix is my favorite way to ... [Read more...]

This will be somewhat shorter summary of the second day of DSC 2014. There was a wider variety of presentations today, but I am only going to discuss those that touched on the main theme of the day, which was … Continue reading → [Read more...]

With the growing popularity of R, there is an associated increase in the popularity of online forums to ask questions. One of the most popular sites is StackOverflow, where more than 60 thousand questions have been asked and tagged to be related to R. On the same page, you can also ... [Read more...]

The Weather Research and Forecasting (WRF) Model is a numerical weather prediction (NWP) system. NWP refers to the simulation and …Sigue leyendo → [Read more...]