In R’s partitioning approach, observations are divided into K groups and reshuffled to form the most cohesive clusters possible according to a given criterion. There are two methods—K-means and partitioning around mediods (PAM). In this article, based on chapter 16 of R in Action, Second Edition, author Rob Kabacoff ... [Read more...]

I recently posted about visualizing the voting patterns of senators. In the post, I scraped voting data for each senator on every vote in the 113th Congress from the Senate website, and then assigned a code of 0 for a no vote on a particular issue, 1 for a yes vote, 2 for ... [Read more...]

With great libraries, just a couple lines of code can do amazing things.  For instance, let’s limit ourselves to less than 10 lines of code and see what ggplot2 and d3 can do.  We will use gridSVG as discussed in yesterday’s post I Want ggplot2/lattice and d3 (gridSVG–... [Read more...]

This guest post is by Punit Kulkarni. Punit is the Director of Marketing at Symphony Analytics and a marketing technology enthusiast. He has helped Fortune 500 retailers and brands in building their customer loyalty programs, direct marketing and business analytics. As a trusted co-marketing partner of Revolution Analytics, Symphony Analytics is ... [Read more...]

Using R, we show how to download historic stock prices for all S&P500 components from Yahoo!Finance. We visualize missing data, and process stock prices to get clean daily logarithmic returns. The data then could readily be used in financial applications like risk management or asset management. [Read more...]

Tracking the job market for statistics, analytics, data mining and the like used to be a major undertaking. However, on November 10, 2011 the world’s largest web site for job postings, Indeed.com, released a tool that allows you to examine trends … Continue reading → [Read more...]

The Joint Statistical Meeting in Montreal has proven to be very good.   Here are a few highlight from Tuesday’s sessions.  There is one major problem that exists and that is there are too many good sessions to attend.  During one time block I had six session that I wanted ... [Read more...]

My last post focused on the use of the ctree procedure in the R package party to build classification tree models.  These models map each record in a dataset into one of M mutually exclusive groups, which are characterized by their average response.  For responses coded as 0 or 1, this average ... [Read more...]

One fascinating thing about working in the area of psychological statistics is how hard it is to move people away from reliance on bad, inefficient or otherwise problematic methods. My own view - informed to some extent by the literature, by experience and by anecdote is that it isn't sufficient ... [Read more...]

This guest post is by Rodolfo Vanzini. Rodolfo is senior partner at eXponential.it — an asset management consultancy based in Italy — and advises clients on investment management issues. He taught at the University of Siena and is an analytics professional. With an economist education and a financial markets expertise four ... [Read more...]

I am currently attending the 2013 Joint Statistical Meeting in Montreal. I will try to share a few if the things that I take away each day. Last night (Monday) I attended the JSM keynote speaker with Nate Silver and it proved to be a very interesting discussion.  Silver is best ... [Read more...]

Recently, I've begun following the Stats Chat blog. Run by the Department of Statistics at the University of Auckland - the largest statistics department in New Zealand or Australia (and the birthplace of R) - this blog apparently started in April of this year.It's aim is:"to foster discussion ... [Read more...]

The other day, there was a bit of a twitter conversation about qqline in R. It made me think: how exactly is the line produced by qqline chosen? I seemed to recall that the line was through the first and third quartiles. An advantage of R is that you can ... [Read more...]

I really like interactive graphics, especially when they come straight from R.  I posted a lot about rCharts, but it is not the only way.  In my mind there are three types of glue to link R to SVG/HTML/Javascript: Let R do the data and then send the ... [Read more...]

Importing tabular data into Julia can be done in (at least) three ways: reading a delimited file into an array, reading a delimited file into a DataFrame and accessing databases using ODBC. Reading a file into an array using readdlm The most basic way to read data into Julia is ... [Read more...]

[Read more...]

I posted about the various googleVis axis options for base charts, such as line, bar and area charts earlier, but I somehow forgot to mention how to set the axes limits.Unfortunately, there are no arguments such as ylim and xlim. Instead, the Google Ch... [Read more...]

# Item equating is the practice of making the results from two # different assessments equivalent. This can be done by either# 1. having the same group take both assessments# 2. having equivalent groups take the different assessments# 3. having non-eq... [Read more...]

Back in May, Twitter's Miguel Rios created some beautiful data visualizations to show that with enough (i.e. billions) of geotagged tweets, you can reveal the geography of where people live, work and commute. Now, a new interactive visualization of 210 million geotagged tweets by AT&T Research Labs reveals the ... [Read more...]

IntroductionLe classifieur naïf bayésien est l'une des méthodes les plus simples en apprentissage supervisé basée sur le théorème de Bayes. il est peu utilisé par les praticiens du data mining au détriment des méthodes traditionnelles que sont les arbres de décision ... [Read more...]